ALDEHYDES, KETONES AND CARBOXYLIC ACIDS
Chapter Outline
10.1 Nomenclature and Structure of Carbonyl Group
10.2 Preparation of Aldehydes and Ketones
10.3 Physical Properties
10.4 Chemical Reactions
10.5 Benzaldehyde
10.6 Nomenclature and Structure of Carboxylic Group
10.7 Preparation of Carboxylic Acids
10.8 Properties of Carboxylic Acids
Carbon compounds containing carbon-oxygen double bond, C = O is called carbonyl group. This is a very important financial group in organic chemistry.
10.1 NOMENCLATURE AND STRUCTURE OF CARBONYL GROUP
Aldehydes and ketones, both have the general formula, CnH2nO, and the common feature of both is carbonyl ( C = O ) group. Therefore, they are called carbonyl compounds. Aldehydes and ketones are the first oxidation products of primary and secondary alcohols, respectively. Aldehyde group is chain terminating group whereas ketonic group is not.
In aldehydes, –CHO group may be attached to a hydrogen atom or alkyl group or aryl group.
Example: HCHO, CH3CHO, CHO
In ketones, ( C = O ) group may be attached to two alkyl groups, two aryl groups, or one alkyl and one aryl group. If both the groups are same, they are simple ketones, and if they are different, they are mixed ketones.
Simple ketones (or) symmetrical ketones:
R–CO–R
Example:
CH3–CO–CH3, C2H5–CO–C2H5, etc.
Mixed ketones or unsymmetrical ketones: R–CO–R'
Example:
CH3–CO–C2H5, CH3–CO–C3H7, etc.
Aromatic ketones : Ar–CO–R
Example: COCH3 , CO etc.
Aldehydes and ketones are widespread in the animal and plant kingdoms. Their role in biochemical processes of life is very important. They are used in many food products and pharmaceuticals. Some of them are used as solvents and as adhesives, paints, resins, perfumes, plastics, fabrics, etc. Some of them are given below:
10.1.1 Nomenclature
There are two systems of naming carbonyl compounds.
Common System
Aldehydes and ketones are often called by their common names. Common names of the aldehydes are derived from the names of the corresponding carboxylic acids by replacing the suffix –ic acid with aldehyde.
The location of the substituent in the carbon chain is indicated by Greek letters α, β, γ, δ, etc. The α–carbon is the one directly linked to the aldehyde group, β–carbon to the next, and so on.
HCOOH (Formic acid) () O ← HCHO (Formaldehyde)
CH3COOH (Acetic acid) () O ← CH3CHO (Acetaldehyde)
CH3CH2COOH () O ← CH3CH2CHO (Propionic acid) (Propionaldehyde)
The common names of ketones are derived by naming two alkyl or aryl groups bonded to the carbonyl group and adding the word ‘ketone’. In case of simple ketones, they are named dialkyl ketones. However, mixed ketones are named by naming the two alkyl groups attached to the ketonic group as separate words in alphabetical order and adding the word ‘ketone’. The locations of substituents are indicated by Greek letters, α, α', β, β', and so on, beginning with the carbon atoms next to the carbonyl group, indicated as α, α'. Alkyl
phenyl ketones are usually named by adding the acyl group as prefix to phenone.
CH3–CO–CH3
Dimethyl ketone (Historical name is acetone)
CH3–CO–C2H5
Ethyl methyl ketone
3 CHCHCOCHCH22 || CC ′′ baab ll
α, β' –dichlorodiethyl ketone
COCH3
Methyl phenyl ketone (or) acetophenone
CO
Diphenyl ketone (or) benzophenone
IUPAC System
Th e IUPAC names of open chain aliphatic aldehydes and ketones are derived from the names of the corresponding alkanes by replacing the ending ‘–e’ with ‘–al’ and ‘–one’, respectively. In case of aldehydes, the longest carbon chain is numbered starting from the carbon of the aldehyde group, while in the case of ketones, the numbering begins from the end nearer to the carbonyl group. The substituents are prefixed in alphabetical order along with numerals indicating their positions in the carbon chain. When the aldehyde group is attached to a ring, the suffix carbaldehyde is added after the full name of the cyclic compound.
The name of the simplest aromatic aldehyde carrying the aldehyde group on a benzene ring is benzene carbaldehyde. However, the common name benzaldehyde is also accepted by IUPAC and so, other aromatic aldehydes are named substituted benzaldehydes.
When three or more aldehyde groups are attached to the unbranched carbon chain, then carbons in the – CHO are not included in the parent carbon chain and carbaldehyde suffix is used for –CHO. All aldehydeic groups are to be given identical treatment.
CH2–CHO
CH–CHO
CH2–CHO 1 2 3 23OCCHCH =−−
Propan-1, 2, 3 – 1 – Phenylpropan –tricarbaldehyde 1 – one (Propiophenone)
The common and IUPAC names of some aldehydes and ketones are given in Table 10.1.
10.1.2 Isomerism
Aldehydes show chain isomerism among the mselves and functional isomerism with
ketones, cyclic ethers, and unsaturated alcohols. They exhibit tautomerism with unsaturated alcohols. Aldehydes with four or more carbon atoms and ketones with five or more carbon atoms show chain isomerism. Ketones may exhibit metamerism.
Chain Isomerism
Example:
Table 10.1 Common and IUPAC names of some aldehydes and ketones
2 CH3CHO
3 (CH3)2CHCHO
4 CH3 CH3–CH2–CH–CH2–CHO β–Methyl valeraldehyde 3–Methylpentanal
5 CH2 = CH – CHO
CH3–CH=CH–CHO
8 CHO Cyclohexane carbaldehyde Cyclohexanecarbaldehyde
9 CHO Br m–Bromobenzaldehyde 3–Bromobenzenecarbaldehyde
10 CHO CHO
Benzene–1, 2–dicarbaldehyde
α, α, α'–Trichlorodiethyl ketone 2, 2, 4–Trichloropentan–3–one
(CH3)2C = CHCOCH3
cyclopentanone 3–Methylcyclopentanone 18. COCH3 Methyl
CO Diphenyl ketone Benzophenone
20. CH2–CO–CH2CH3 Ethylbenzyl ketone 1–Phenylbutan–2–one
21. 23 O || CCHCH
10.1.3 Structure of Carbonyl Group
Ethyl phenyl ketone (Propiophenone) 1-Phenylpropan-1-one
Both aldehydes and ketones have carbonyl group as the functional group. The carbonyl carbon is sp2 hybridised and, thus, it has three sp2 hybrid orbitals and one unhybridised p–orbital. It uses sp 2 hybrid orbitals to form three sigma bonds, one with oxygen atom and remaining two with two other atoms or groups (R or H). The bond angles are
approximately 120°, as expected of a trigonal coplanar structure.
π-bond
C O
σ-bond
The unhybridised p–orbital of carbonyl carbon forms pi bond with oxygen atom by sideway overlapping with half filled p–orbital of oxygen
phenyl ketone Acetophenone 19.
atom. In formaldehyde, HCH bond angle is slightly less than that of HCO bond angle, because double bond single bond repulsion is stronger than single bond single bond repulsion. The carbon–oxygen double bond is polarised due to higher electronegativity of oxygen relative to carbon. Consequently, oxygen attains a partial negative charge and carbon attains a partial positive charge, making the bond polar. Hence, the carbonyl carbon is an electrophilic (Lewis acid), and carbonyl oxygen, a nucleophilic (Lewis base) centre. The higher values of dipole moments of carbonyl compounds than the corresponding ethers and the high polarity of the carbonyl group is explained on the basis of resonance, involving a neutral and a dipolar structure.
TEST YOURSELF
1. The hybridisation of carbon in the carbonyl group is
(1) sp3 (2) sp2
(3) sp (4) sp3d
2. 2-pentanone and 3-pentanone are (1) positional isomers
(2) functional isomers
(3) metamers
(4) ring chain isomers
3. Vinyl alcohol and ethanal are (1) metamers
(2) tautomers
(3) position isomers
(4) chain isomers
4. Which type of isomerism is shown by pentanone?
A) Chain
B) Position
C) Functional
(1) A only (2) B only
(3) C only (4) A, B and C
5. The most polar compound among the given carbonyl compounds is
(1) propanone (2) formaldehyde (3) propanal (4) hexan-3-one
6. IUPAC name of 3 CClCHO is (1) chloral (2) trichloro acetaldehyde (3) 1, 1, 1-trichloroethanal (4) 2, 2, 2-trichloroethanal
7. The number of structurally isomeric ketones with formula C6H12O is (1) six (2) two (3) five (4) four
8. In aldehydes, – CHO may be attached to (1) alkyl group only (2) H atom only (3) aryl group only (4) alkyl /aryl /H-atom
Answer Key
(1) 2 (2) 3 (3) 2 (4) 4 (5) 2 (6) 4 (7) 1 (8) 4
10.2 PREPARATION OF ALDEHYDES AND KETONES
Carbonyl compounds can be prepared from various compounds, like alcohols, nitriles, esters, hydrocarbons, etc.
10.2.1 Preparation from Alcohols
Oxidation: Aldehydes can be prepared by the regulated oxidation of primary alcohols. Oxidation may be carried out by acidified solution of potassium dichromate, or potassium permanganate, or manganese dioxide. The reaction is controlled by distilling out aldehyde as soon as it is formed, as aldehydes are very susceptible to further oxidation to carboxylic acids.
RCH2OH + (O) →RCHO + H2O
CH3CH2OH + (O)→CH3CHO + H2O
Pyridinium chloro chromate (PCC): C 5 H 5 N + HCrO3Cl–, or Collin’s reagent, is a good oxidising agent for converting primary alcohols to aldehydes and secondary alcohols to ketones. Collin’s reagent is used in nonaqueous medium, dichloromethane.
Tertiary alcohol gives alkene through E 2 pathway.
33 3 OH | CHCCH | CH 0 AgorCu 300C → 32 3 CHCCH | CH −=
From Nitriles and Esters
Pyridinium dichromate (PDC), (C 5 H 5NH) 2Cr 2O 7, can also be used in place of PCC.
Jones reagent: CrO3 + H2SO4 + H2O in acetone is called Jones reagent. It can oxidise 1° alcohol to acid and 2° alcohol to ketones.
An alkyl cyanide is dissolved in ether and reduced with stannous chloride and hydrochloric acid. The iminochloride thus formed gets hydrolysed to give aldehyde.
22 SnCl HO HCl RCNRCHNH −≡→−=→ RCHO + NH4Cl
This reaction is called Stephen reaction. This method is for preparing only aldehydes. Alternatively, nitriles are selectively reduced by di-isobutylaluminium hydride, (DIBAL–H) to imines, followed by hydrolysis to aldehydes.
CH3CN 2 (i)DIBALH (ii)HO → CH3CHO
Catalytic Dehydrogenation
When vapours of a primary or a secondary alcohol are passed over copper or silver catalyst at 300°C, dehydrogenation takes place and an aldehyde or a ketone is formed, respectively.
o Cu(or)Ag 22 300C RCHOH RCHOH−→−+
CH3–CH=CH–CH2–CH2–CN 2 (i)DIBALH (ii)HO →
CH3–CH=CHCH2CH2CHO
Similarly, esters are also reduced to aldehydes with DIBAL-H.
CH3COOC2H5 2 (i)DIBALH (ii)HO → CH3CHO
CH3(CH2)9COOC2H5 (i) (ii)→CH3(CH2)9CHO
RCHOHR RCORH′′ −−→−−+
() 0 CuorAg 32 32 300C CHCHOH CHCHOH→+ () 0 CuorAg 2 300C
() o CuorAg 33 332 300C CHCHOHCH CHCOCHH→+
In the presence of these catalysts, if air is present, water is formed along with carbonyl compound. The dehydrogenation reaction is a better method of preparation because there is no risk of further oxidation of aldehyde or ketone.
CH3CH2OH () AgorCu air → CH3CHO + H2O
CH3CHOHCH3 () AgorCu air → CH 3COCH3 + H2O
DIBAL-H shows the temperature dependency. Esters are reduced to aldehydes at lower temperature, but at normal temperature, reduction gives alcohol.
Reductive Ozonolysis of Alkenes
Alkenes add on ozone to form unstable ozonide which, when decomposed by passing hydrogen in the presence of zinc dust and water, aldehyde or ketone or both are formed, depending upon the structure of alkene. R – CH = CH – R + O3 2 Zn,HO → 2RCHO + H2O
2 Zn,HO 3 CHCH=CHCH+O33−−→ 32 2CHCHO+HO R RC=C R' R' +O3 → 2 HO,Zn R R CO + OC + H2O2 R' R' C=C CH3 CH3 CH3 CH3 +O3 → 2 HO,Zn 2CH 3COCH3 + H2O2
In place of zinc, we can also use CH 3–S–CH3 (DMS) and PPh3 33 (DMS) S || CHCCH HO22 → 33 (DMSO)
|| CHSCH +H2O PPh 3 HO22 → 3 O || PPh +H2O
From Alkynes
Addition of water to alkynes in the presence of sulphuric acid and mercuric sulphate gives aldehydes or ketones.
Acetaldehyde is obtained by passing acetylene gas through an aqueous solution of 40% sulphuric acid and 1% mercuric sulphate at 60°C. An unstable enol, vinyl alcohol, is formed as intermediate.
HC ≡ CH + H 2 O →[CH 2 =CH(OH)] CH3CHO
Acetone is obtained by passing propyne into an aqueous solution of 40% sulphuric acid and 1% mercuric sulphate at 60°C. An unstable enol, propenol–2, is formed as intermediate.
CH3–C ≡ CH+H2O→[CH3–C(OH)=CH2]→ CH3–CO–CH3
From Gem-Dihalides
Aldehydes are obtained by alkaline hydrolysis of terminal gem–dihalides
CH3CHCl2 2KOH 2KCl → CH3CH(OH)2 2 HO → CH 3CHO
Ketones are formed by hydrolysis of non terminal gem–dihalides.
–2KCl –H2O
This method is not used much since aldehydes are affected by alkali and dihalides are usually prepared from the carbonyl compounds.
From Grignard Reagent
Grignard reagents give aldehydes with hydrogen cyanide and ketones with alkyl cyanides.
R–C ≡ N + RMgX→R– C | R =NMgX
2 2HO → R– C | R =O + NH3 + Mg(OH)X
CH3–C ≡ N + CH3MgI 2 2HO →
CH3–3 C=O | CH + NH3 + Mg(OH)I
Alkyl cyanides react with Grignard reagent in ether solvent to form an addition compound, which on acid hydrolysis, gives a ketone.
CH3CH2 – C ≡ N + C6H5 MgBr ether → NMgBr
3 HO 32 CHCHC + −→
65CH O
32 CHCHC
65CH
Propiophenone
10: Aldehydes, Ketones and Carboxylic Acids
From Acid Chlorides
Acid chlorides can be reduced into aldehydes with hydrogen over catalyst palladium supported on barium sulphate. This reaction is called Rosenmund reduction. Ketones cannot be prepared by this method.
RCOCl + H2 4 Pd BaSO → RCHO + HCl
CH3COCl + H2 4 Pd BaSO → CH3CHO + HCl
Treatment of acyl chlorides with dialkyl cadmium, prepared by the reaction of cadmium chloride with Grignard reagent, gives ketones.
2R MgX + CdCl2→R2Cd + 2Mg(X)Cl
2R'–CO–Cl + R2Cd→2R'–CO–R+CdCl2
2CH3COCl+(CH3)2Cd→ 2CH3COCH3 + CdCl2
R 2 Cd only react wi th acid halide due to less polarity of R–Cd bo nd and more
el ectrophilicity of carbonyl carbon in acid halide O || (RCCl).
From Carboxylic Acids
By heating a mixture of the calcium salts of formic acid and any one of its homologues, aldehyde is formed.
over manganous oxide as catalyst at 300°C, aldehyde is formed.
RCO2H + HCO2H MnO → RCHO + CO2 + H2O
R2CO is obtained as byproduct. The reaction proceeds via the manganous salt.
By heating the calcium salt of any monocarboxyllic acid other than formic acid, ketone is formed.
2R C H
+ 2CaCO3
By passing a mixture of the vapours of formic acid and any one of its homologues
If mixture of calcium salts is used, mixed ketones are obtained.
(R1CO2)2 Ca + (R2CO2)2 Ca →2R1COR2+2CaCO3
By passing the vapour of any monocarboxylic acid other than formic acid over managanous oxide at 300°C, ketone is form ed. MnO 2 222 2RCOHRCOCOHO →++
1. How is acetone obtained from isopropyl bromide?
Sol. Step - I: Isopropyl bromide is converted into isopropyl alcohol, by hydrolylis with aq. KOH.
Step - II: Isopropyl alcohol is converted into acetone by dehydrogenation, using copper.
Br aq. KOH
Try yourself:
1. () XY aq.KOH Cu,300C 25 CHCHBrCH25 ° →→ () XY aq.KOH Cu,300C CHCHBrCH25 °
In this reaction, identify the organic compounds X and Y formed, giving their systematic names.
Ans: X is penta–3–ol and Y is pent–3–one
TEST YOURSELF
1. X 32 3 CHCHOHCHCHO → , here X is / are
(A) Cu/573K
(B) Ag/573 K (C) PCC
(D) CrO3+H2SO4 (E) C6H5N2+Cl
(1) D only (2) A, D and E only (3) B and E only (4) A and E only
2. The most suitable reagent for the conversion of 2 RCHOHRCHO → is (1) K2Cr2O7 (2) CrO3 (3) KMO4 (4) PCC
3. In which of the following processes is acetone one of the final products?
(1) Ozonolysis of ethyne (2) Oxidation of 2-butene with KMnO4/H+ (3) Oxidation of 2, 3 -dimethyl -2-butene with KMnO4/H+;∆ (4) Dehydrogenation of 1-propanol
4. 2, 3 - dimethyl - 2 - butene, on reductive ozonolysis, gives (1) acetone (2) acetaldehyde (3) butanone (4) formaldehyde
5. X 32 32 CHCHCNCHCHCHO. −≡→
The reagent X is (1) SnCl2/HCl/H2O, (2) H2/Pd−BaSO4
(3) LiAIH4/ether (4) NaBH4 /ether/H3O+
6. Which of the following, on heating with aqueous KOH, produces acetaldehyde?
(1) CH3COCl (2) CH3CH2Cl
(3) CH2ClCH2Cl (4) CH3CHCl2
7. Rosenmund’s reduction is used for the preparation of
(1) carboxylic acid (2) aldehydes (3) esters (4) carbohydrates
8. The first oxidation product of which of the following alcohols is a ketone with the same number of carbon atoms?
(1) CH3CH2CH2OH (2) (CH3)2CHCH2OH (3) CH3CH(OH)CH3 (4) (CH3)3C - OH
9. 2 3 1)SnClHCl 2HO RCN RCHO + + −→−
This reaction is known as (1) Rosenmund (2) Williamson (3) Stephen (4) Kolbe
10. Ketones cannot be prepared in one step from (1) Alcohols (2) Alkenes (3) Alkynes (4) Esters
Answer Key
(1) 1 (2) 4 (3) 3 (4) 1 (5) 1 (6) 4 (7) 2 (8) 3 (9) 3 (10) 4
10.3 PHYSICAL PROPERTIES
At ordinary temperature, formaldehyde is a gas, while next ten members of the aldehyde series are colourless volatile liquids. Ketones up to eleven carbon atoms are also colourless volatile liquids. The higher members of both the series are solids.
The lower members of aldehydes and ketones, such as formaldehyde, acetaldehyde,
10: Aldehydes, Ketones and Carboxylic Acids
and acetone are miscible with water in all proportions, because they form hydrogen bond with water.
The solubility of these compounds in water decreases with the increase in the size of the alkyl group. It is due to the hydrophobic nature of the alkyl group. All aldehydes and ketones are fairly soluble in organic solvents, like benzene, ether, chloroform, etc.
Lower aldehydes have unpleasant sharp pungent odours. As the size of the molecule increases, the odour becomes less pungent and more fragrant. Many naturally occurring carbonyl compounds are used in the blending of perfumes and flavouring agents. Acetone is a highly inflammable liquid.
Aldehydes and ketones have relatively high boiling points, as compared to hydrocarbons or ethers of comparable molecular masses. It is due to appreciable intermolecular (dipole–dipole) attraction, as the aldehydes and ketones are polar molecules. These dipole–dipole interactions are, however, weaker than intermolecular hydrogen bonding in alcohols. Consequently, boiling points of aldehydes and ketones are relatively lower than those alcohols of comparable molecular masses. The following compounds have almost same molecular mass (58–60). Their boiling points order is: 1–propanol (alcohol, 370 K) > propanone (ketone, 329 K) > propanal (aldehyde, 322 K) > methoxy-ethane (ether, 281 K) > butane (alkane, 273 K).
TEST YOURSELF
1. Highest boiling point is observed for (1) methoxy ethane
(2) acetone
(3) propanal
(4) propan-1-ol
2. False statement among the following is (1) formaldehyde is soluble in water
(2) acetic acid exists as dimer in benzene
(3) acetone is a pleasant smelling liquid
(4) acetaldehyde is insoluble in water
3. Which of the following gives a crystalline compound with (1) HCN (2) NaHSO3
(3) RMgX (4) ROH
4. Identify the correct order of boiling points of the following compounds.
A) CH3CH2CH2CH2OH
B CH3CH2CH2CHO
C) CH3CH2CH2COOH
(1) A > B > C
(2) C > A > B
(3) A > C > B
(4) C > B > A
5. Choose the correct statements among the following.
A) Methanal is a gas at room temperature.
B) Ethanal is a volatile liquid.
C) Methanal, ethanol, and propanone are soluble in water.
D) Higher aldehydes are pungent smelling.
(1) All
(2) A, B, C only
(3) B, C, D only
(4) A, B, D only
Answer Key
(1) 4 (2) 4 (3) 2 (4) 2
(5) 2
10.4 CHEMICAL REACTIONS
Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons.
Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon than in aldehydes having only one substituent.
The reactivity of the carbonyl group towards the addition reactions depends upon the magnitude of the positive charge on the carbonyl carbon atom. Any substituent that increases the positive charge on the carbonyl carbon must increase its reactivity towards addition reactions. The introduction of electron withdrawing group (–I effect) increases the reactivity, while introduction of alkyl group decreases the reactivity, as +I effect and steric hindrance increase.
Reactivity order of carbonyl compounds:
Nucleophilic Addition Reactions
The carbonyl group is a highly polar group as the p –electrons of the double bond are shifted to the more electronegative oxygen atom.
Chloral is more reactive than acetaldehyde as chlorine atoms increase the positive charge on the carbonyl carbon.
Th us, the carbonyl group has two active centres which can be easily attacked. The positively charged carbon is readily attacked by electron rich nucleophiles. The negatively charged oxygen is attacked by electron deficient electrophiles. However, during addition reaction, nucleophilic attack occurs because the anion produced is more stable than the cation.
In the first step, planar sp2 hybridised carbon changes to sp 3 and a tetrahedral alkoxide intermediate is produced. This intermediate captures a proton from the reaction medium to give the electrically neutral product. If nucleophile is weak, the reaction requires an acid catalyst.
Mechanism of nucleophilic addition under acidic conditions:
10.4.1 Nucleophilic Addition Reactions
A ldehydes and ketones are highly reactive compounds. Since both possess the same carbonyl functional group, they undergo similar chemical reactions. The characteristic reactions of aldehydes and ketones are nucleophilic addition reactions.
I n acidic conditions, the first step plays an important role. Specially, protonating the carbonyl group generates a very powerful electrophile.
It is true that the carbonyl group is already a fairly strong electrophile. However, a protonated carbonyl group bears a full positive charge, rendering the carbon atom even more electrophilic. This is especially important when weak nucleophiles, such as H2O or ROH, are employed.
Hydrate Formation
When an aldehyde or ketone is treated with water, the carbonyl group can be converted into a hydrate.
Mechanism of acid-catalysed hydration:
The position of equilibrium generally favours the carbonyl group rather than the hydrate, except in the case of very simple aldehydes, such as formaldehyde.
Formaldehyde reacts with water so readily because its substituents are very small. Electric effects can also favour reaction with nucleophiles. Electronegative atoms, such as halogens attached to the carbon atoms next to the carbonyl group, can increase the extent of hydration according to the number of halogen substituents and their electronwithdrawing power. They increase the polarisation of the carbonyl group, which already has a positively polarised carbon. Trichloroacetaldehyde (chloral, Cl3CHO) is hydrated completely in water, and the product ‘chloral hydrate’ can be isolated as crystals and is an a naesthetic.
Addition of Hydrogen Cyanide
Both aldehydes and ketones react with hydrogen cyanide (sodium cyanide and dilute sulphuric acid) to form cyanohydrins. The reaction occurs very slowly with pure hydrogen cyanide. It is catalysed by a base and the generated cyanide ion, being a strong nucleophile, readily adds on to carbonyl compounds. Cyanohydrins are useful synthetic intermediates.
The rate of reaction is relatively slow under neutral conditions but is readily enhanced in the presence of either acid or base. That is, the reaction can be either acid catalysed or base catalysed, allowing the equilibrium to be achieved much more rapidly.
Addition of Sodium Bisulphite
Crystalline solid derivatives are formed when aldehydes or ketones are shaken with saturated aqueous solution of sodium bisulphite. This reaction is used in the separation of aldehydes and ketones from non-carbonyl compounds. Being a reversible reaction, the addition compounds can be decomposed by dilute mineral acids or aqueous alkalis to regenerate the original aldehyde or ketone. This reaction can be used for separation and purification of aldehydes and methyl ketones.
3 HC 3 HC 3 OH CONaHSO C =+→ H H 3 SONa Acetaldehyde sodium bisulphite
3 HC 3 HC 3 OH CONaHSO C =+→
3 HC 3 H C 3 SONa Acetone sodium bisulphite
The position of the equilibrium lies largely to the right hand side for most aldehydes and to the left for most ketones, due to steric reasons. The hydrogen sulphite addition compound is water soluble and can be converted back to the original carbonyl compound by treating it with dilute mineral acid or alkali. Therefore, these are useful for separation and purification of aldehydes.
Addition of Grignard Reagent
Aldehydes and ketones react with Grignard reagent to from an adduct, which on hydrolysis, yields the corresponding alcohols. 2
(Primary alcohol)
alcohol)
(Tertiary alcohol)
The reaction of Grignard reagent with methanal produces a primary alcohol, with other aldehydes, a secondary alcohol, and with ketone, a tertiary alcohol.
Addition of Alcohols
Aldehydes react with alcohols in the presence of dry HCl gas to form acetals. In this reaction, the addition of one molecule of alcohol to one molecule of aldehyde results in the formation of a hemiacetal. A hemiacetal contains both an ether as well as alcohol functional groups. It is an unstable compound and cannot be isolated. It further reacts with alcohol to form stable acetal. Acetals are dialkoxy compounds (geminal diethers) and have properties similar to ethers.
10: Aldehydes, Ketones and Carboxylic Acids
Ketones react with ethylene glycol under similar conditions to form cyclic products known as ethylene glycol ketals. Dry HCl protonates oxygen of C=O and increases the electrophilicity of the carbonyl carbon, facilitating the nucleophilic attack of ethylene glycol.
Ethylene glycol ketal
Acetals and ketals are hydrolysed with aqueous mineral acids to yield corresponding aldehydes and ketones, respectively. Ketones do not ordinarily react with monohydric alcohols.
Addition of Ammonia
Ammonia reacts with aldehydes (except formaldehyde) and ketones to form the products called imines. Acetaldehyde reacts with ammonia to form acetaldiamine ammonia and loses a molecule of water to form ethanalimine.
10.4.2 Nucleophilic Addition Elimination Reactions
Carbonyl carbon, being electrophilic can be attacked by nucleophile, then the resultant substance may undergo elemination. This reaction is found with derivatives of ammonia.
Reaction with Ammonia Derivatives
Aldehydes and ketones react with a number of ammonia derivatives to form compounds containing carbon nitrogen double bonds with elimination of water molecule. These reactions are called condensation reactions.
Important derivatives of ammonia:
■ Hydroxyl derivative of ammonia is hydroxylamine.
■ Amino derivative of ammonia is hydrazine.
■ Phenyl derivative of hydrazine is phenyl hydrazine.
■ 2, 4-dinitrophenyl derivative of hydrazine is 2, 4–dinitrophenyl hydrazine.
■ Amido derivative of hydrazine is semicarbazide.
In general, if we represent these derivatives by H 2 N–G, then their reaction with aldehydes and ketones can be represented as follows:
The condensation products of aldehydes or ketones,
Ketones form complex ketonic amines. Acetone reacts with ammonia to form acetone ammonia which loses a molecule of water to form propanonimine. Alkanamines are unstable. Imines on hydrogenation in the presence of Ni catalyst give alkanamines.
■ with hydroxylamine are called oximes,
■ with hydrazine are called hydrazones,
■ with phenyl hydrazine are called phenyl hydrazones,
■ with 2, 4–dinitrophenyl hydrazine are called 2, 4–dinitrophenyl hydrazones, and
■ with semicarbazide are called semicarbazones.
The various ammonia derivatives and their reaction products with carbonyl compounds
are summarised in Table 10.2. For carrying out these reactions, the medium should be slightly acidic. The optimum pH of the medium is around 3.5. It should not be strongly acidic. Reactions of the above type are basically addition reactions but pro ceed with the elimination of simple molecules, like water. Hence, they are called condensation reactions. 3 HC 2 COHNOH H =+→
2. Out of two –NH2 groups of semicarbazide, only one is involved in the formation of semicarbazone. Explain.
Sol. The lone pair of electrons of –NH 2 group attached to O || C is involved in conjugation with the p –electrons of C=O. As a result, the electron pair of the –NH2 group is not available for nucleophilic attack on carbonyl carbon whereas other terminal –NH2 group is free to attack the carbonyl carbon.
Substituted imine (Schiff’s base)
NH2NHC6H5
2, 4–Dinitrophenylhydrazine (DNP/ DNPH),
O N2 H2NH NO2 (Brady’s reagent/ Bosche’s reagent) C=NNHNO2
O2 2, 4–Dinitro–phenylhydrazone –NHCONH2 Semicarbazide, NH2NHCOHN2 C NNHCONH2 Semicarbazone
Table 10.2 Ammonia derivatives and their products with carbonyl compounds
Try yourself:
2. How-many C–N sigma bonds are found in acetaldehyde–2, 4–dinitrophenyl hydrazone?
Ans: Four
10.4.3 Reduction
Reduction to alcohols: Aldehydes and ketones, on mild reduction, give primary and secondary alcohols, respectively. This type of reduction is carried out either catalytically with hydrogen in the presence of Ni, Pt, or Pd, or chemically with lithium aluminium hydride, or sodium borohydride, or sodium in ethanol. Ni 22 RCHOHRCHOH +→
CH3CHO + H2 Ni → CH3CH2OH () Ni 2 RCORHRCHOHR +→
CH3COCH3 + H2 Ni → CH3CH(OH)CH3
Reduction to hydrocarbons: The carbonyl group can be reduced to methylene group, resulting in the formation of alkanes by any one of the following reagents.
Clemmensen’s reduction: Carbonyl compounds are reduced to alkanes using zinc amalgam and concentrated hydrochloric acid.
R – CHO + 4(H)→ R – CH 3 + H2O
CH3CHO + 4(H) → CH3–CH3 + H2O
R – CO – R + 4(H) → R – CH2 – R + H2O
CH3COCH3 + 4(H) → CH3CH2CH3 + H2O
General features of the reaction:
■ Clemmensen reduction of acid-sensitive substrates and polyfunctional ketones is rarely successful in yielding the expected alkanes.
■ Selective reduction of aldehydes or keto groups is not possible by this method on compounds containing other functional groups, which can be reduced by metal and acids.
Wolff Kishner reduction: Carbonyl compounds are reduced to alkanes using hydrazine, followed by heating with sodium or potassium hydroxide in high boiling solvent, such as ethylene glycol.
R – CHO + NH2NH2→ R – CH3 + H2O + N2
CH3CHO + NH2NH2 KOH 180-200°C → CH3 – CH3 + H2O + N2
R – CO – R + NH2NH2→ R – CH2 – R + H2O + N2
H3COCH3+NH2NH2 KOH boil →
CH3CH2CH3 + H2O + N2
General features of the reaction:
■ Esters, lactones, amides, and lactams are hydrolysed under the reaction conditions.
■ Sterically hindered carbonyl compounds are deoxygenated more slowly than unhindered ones, so higher reaction temperatures are required.
■ Can’t be used for a,b-unsaturated carbonyl compounds
Bimolecular reduction: Two molecules of ketones undergo reduction in the presence of Hg/Mg to form pinacol. Upon treatment with mineral acids, pinacol is converted into pinacolone.
This transformation involves dehydration and rearrangement is called pinacolpinacolone rearrangement.
H3C 2 H3C Acetone H3C H3C O C C CH3 CH3 MgHg benzene heat CO=→ O Mg
HO → 2, 3-Dimethylbutan -2,3-diol (pinacol) OH C CH3 OH C CH3 H3C H3C
Meerwein Ponndorf Verley (MVP) reduction: Aldehydes and ketones can be reduced to corresponding alcohols by heating them with aluminium isopropoxide in excess of isopropyl alcohol. This reaction is highly specific. The other functional groups, such as carbon-carbon double bond or nitro group, remain unaffected. The co-product, acetone, is continuously distilled off to drive the equilibrium in favour of the alcohol product.
[RCHO + 2[Ag(NH3)2]+OH–→
32 RCOOH2Ag4NHHO] +↓++
CH3CHO+ Ag2O →CH3COOH + 2Ag ↓ (Black)
CH3CHO + 2[Ag(NH3)2]OH→
CH3COONH4+2Ag ↓ (Black)+3NH3 +H2O
The following compounds give silver mirror test.
10.4.4 Oxidation
Oxidation of aldehydes: Aldehydes are easily oxidised and thus act as strong reducing agents. They are oxidised to the corresponding carboxylic acids containing the same number of carbon atoms. The oxidation of aldehydes does not involve the cleavage of carboncarbon bond. Since aldehyde group is chainterminating group, it is easily oxidised by even mild oxidising agents like Tollens’ reagent, Fehling’s solution, or Benedict’s solution, along with strong oxidising agents, like nitric acid, acidified potassium permanganate, or potassium dichromate.
Oxidation with Tollen’s Reagent
Tollen’s reagent is ammoniacal solution of silver nitrate. On warming with this reagent, aldehydes form a silver mirror on the walls of the container. The reaction is also known as silver mirror test for aldehydes.
RCHO + Ag2O→RCOOH + 2Ag ↓ (Black)
Oxidation with Fehling’s Solution
Fehling’s solution is an alkaline solution of cupric ion complexed with sodium potassium tartarate (Rochelle salt). Fehling’s solution A is freshly prepared alkaline copper sulphate and Fehling’s solution B is sodium potassium tartarate. These two solutions are mixed in equal amounts, called Fehling’s reagent. On heating an aldehyde (called Fehling’s solution) with Fehling’s reagent, a reddish brown precipitate is obtained. Aromatic aldehydes do not respond to this test.
RCHO + 2CuO→RCOOH + Cu 2O ↓ (Brick red)
RCHO + 2Cu2+ + 5OH–→
RCOO– + 3H2O + Cu2O ↓
CH3CHO+2CuO→CH3COOH + Cu2O ↓ (Brick red)
Benedict’s solution is a mixture of solutions of copper sulphate, sodium citrate, and sodium carbonate. The reaction of aldehydes with Benedict’s solution is same as that with Fehling’s solution. Aldehydes reduce Benedict’s solution to give reddish brown precipitate. Aromatic aldehydes reduce Tollens’ reagent, but not Fehling’s solution or Benedict’s solution.
Oxidation of ketones: Ketones are generally oxidised under vigorous conditions, with strong oxidising agents, like concentrated nitric acid, acidified potassium permangate, or acidified potassium dichromate. Oxidation of ketones involves cleavage of bond between carbonyl carbon and a–carbon on either side of keto group, giving a mixture of carboxylic acids having lesser number of carbon atoms. (Popoff’s rule).
CH3–CO–CH3 3 (O) Conc.HNO
HCOOH + CH 3COOH
R1COOH + R2CH2COOH
(Breakage of C1 – C2 bond)
R1CH2COOH + R2COOH
(Breakage of C2 - C3 bond)
Since ketones are not oxidised by mild oxidising agents, they do not reduce Tollen’s reagent, Fehling’s solution, and Benedict’s solution. Hence, these reagents are used to distinguish between aldehydes and ketones.
Oxidation with sodium hypohalite:
Acetaldehyde and ketones having at least one methyl group linked to the carbonyl carbon atom (methyl ketones) are oxidised by sodium hypohalite to sodium salts of corresponding carboxylic acids having one carbon atom less than that of carbonyl compound. The methyl group is converted to haloform. This oxidation does not affect a carbon-carbon double bond, if present in the molecule.
Iodoform reaction with sodium hypoiodite is also used for the detection of CH3CO group or CH3CH(OH) group, which produces CH3CO group on oxidation.
3. When a few millilitres of Tollen’s reagent is added to a test tube A and the contents are warmed, a silver mirror is formed. But when the same reagent is added to another test tube B, silver mirror is not formed in the same manner. Both the compounds in A and B have the same formula, C3H6O. Solve it.
Sol. Tollen’s reagent is ammoniacal silver nitrate, [Ag(NH3)2] NO3. It is a mild oxidising agent (E° (Ag(NH3)2+ / Ag = + 0.15 V).
Hence, it can oxidise only aldehydes but not kentones.
So, the test tube A must be having the propionaldehyde (CH3CH2CHO) but test tube B must have acetone (CH3–CO–CH3).
Try yourself:
3. With Fehling’s solution O xidation of the compound O CHO gives a salt, X. Wha t is the organic anion of the salt?
Ans: 4–Oxocyclohexane carboxylate anion
10.4.5 Other Reactions
a –Hydrogen atoms of carbonyl compounds are acidic in nature due to the strong electron withdrawing effect of the carbonyl group and resonance stabilisation of the conjugate base. The aldehydes and ketones undergo a number of reactions due to the acidic nature of a –hydrogen.
Aldol Condensation
Aldehydes: Two molecules of an aldehyde having at least one a–hydrogen atom undergo condensation in the presence of dilute alkali, such as NaOH, Ba(OH) 2 or K 2CO 3, etc., to form b –hydroxy aldehydes (aldol). This is known as aldol reaction. The aldols lose water to give a,b–unsaturated carbonyl compounds, which are aldol condensation products, and the reaction is called aldol condensation.
Carbonyl compounds that do not contain a–hydrogen atoms, like formaldehyde, benzaldehyde, etc., do not undergo this reaction.
Crossed Aldol Condensation
When aldol condensation is carried out between two different aldehydes or ketones, if both of them contain a –hydrogen atoms, a mixture of four different products is formed. Two of them are called cross aldols. The following reactions take place when acetaldehyde and propionaldehyde condense together.
2CH3CHO→CH3–CH=CH–CHO
But-2-enal
2CH3CH2CHO→CH3–CH2–CH=C(CH3) CHO
2-Methylpent-2-enal
CH3CHO + CH3CH2CHO →
CH3 – CH = CH – CHO + But-2-enal (Self aldol product)
CH3 – CH2 – CH = C(CH3) CHO
2-Methyl pent-2-enal (Self aldol product)
CH3–CH=C(CH3)CHO+CH3–CH2–CH=CH–CHO
2-Methylbut-2-enal Pent-2-enal (cross aldol) (cross aldol)
In cross aldol reaction, ketones can also be used as one component.
Cannizzaro Reaction
Ketones: In the presence of Ba(OH)2, acetone undergoes condensation and gives diacetone alcohol. A b-hydroxy ketone (ketol) is formed.
2CH3COCH3 Ba(OH)2
2 HO D
(CH3)2C(OH)–CH2COCH3
Diacetone alcohol
(CH3)2C=CHCOCH3
Mesityl oxide
Aldehydes that do not have an a –hydrogen atom undergo self oxidation and reduction (disproportionation) reaction on treatment with concentrated alkali. In this reaction, one molecule of aldehyde is reduced to alcohol while another is oxidised to acid salt. When formaldehyde is treated with concentrated alkali, one molecule is reduced to methyl alcohol while another is reduced to formic acid salt.
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
HCHO + HCHO + KOH KOH → CH3OH + HCOOK
Isobutyraldehyde, although it possesses an alpha hydrogen, underegoes Cannizzaro reaction. 200ºC
32 2(CH)CHCHONaOH Isobutyraldehyde +→
322 (CH)CHCHOH Isobutylalcohol + 32 (CH)CHCOONa sodiumisobutyrate
Though Cl 3 C–CHO and (C 6 H 5 ) 3 C – CHO have no alpha hydrogen, they cannot undergo Cannizzaro reaction.
Reaction:
Mechanism:
When concentration of OH is low, the rate = k[Substrate]2 [ OH ].
When concentration of –OH is high, the rate = k[Substrate]2 [–OH]2
Other examples:
Crossed Cannizzaro Reaction
In crossed Cannizzaro reaction, the more reactive aldehyde undergoes oxidation and forms salt of carboxylate, whereas less reactive aldehyde undergoes reduction and forms alcohol.
CH2OH Δ KOH HCOO– + +HCHO
Intramolecular Cannizzaro Reaction
CH2OH
COONa Δ NaOH
4. When benzaldehyde and acetaldehyde mixture is treated with dil. NaOH at normal temperature, immediately, cinnamaldehyde (C 6 H 5 –CH=CHO) is formed. How is it formed?
Sol. The reaction between benzaldehyde and acetaldehyde under the influence of dil. NaOH is crossed aldol condensation.
C6H5 – CHO + CH3 – CHO
The initial aldol product undergoes dehydration readily, as the final product, a,b –unsaturated carbonyl compound has conjugation of C = C of benzene ring with the carbonyl group | CO−=
Try yourself:
4. What is the common name of the product of crossed aldol condensation product formed, when benzaldehyde and acetophenone are involved?
Ans: Benzalacetophenone, 65 65 O || CHCHCHCCH −=−−
Haloform Reaction
Compounds containing methyl ketonic group (CH3CO–) undergo haloform reaction. Both acetaldehyde and acetone respond to haloform reaction when treated with halogen and alkali. Halogen can be chlorine, bromine, and iodine.
CH3CHO + 3X2 + 4NaOH →
HCOONa + CHX3 + 3H2O + 3NaX
CH3COCH3 + 3X2 + 4NaOH →
CH3COONa + CHX3 + 3H2O + 3NaX
CHI3 is a yellow precipitate.
10.4.6 Tests for Carbonyl Compounds
Carbonyl compounds give orange, red, and yellow coloured needle type crystals with 2, 4–dinitrophenyl hydrazine, called Bosche’s reagent or Brady’s reagent. Then, aldehydes and ketones are differentiated with other reagents.
■ Aldehydes give silver mirror (black precipitate) with Tollens’ reagent, but not ketones.
■ Aldehydes give red precipitate with Fehling’s solution, but not ketones.
■ Aldehydes give red precipitate with Benedict’s solution, but not ketones.
■ Aldehydes restore the pink colour of Schiff’s base, but not ketones.
Schiff’s reagent is p–rosaniline hydrochloride (pink/magenta dye) aqueous solution decolourised by sulphur dioxide.
10.4.7
Uses of Carbonyl Compounds
■ Acetaldehyde is used in the preparation of acetic acid, acetic anhydride, ethyl acetate, vinyl acetate, chloral, 1, 3– butadiene, polymers, dyes, and drugs.
■ Acetaldehyde is used as an antiseptic inhalent in nose troubles.
■ Acetone and ethylmethy ketones are used as solvents for cellulose acetate, cellulose nitrate, resins, etc.
■ Acetone is used for storing acetylene gas and its transportation.
■ Acetone is used in the preparation of chloroform, iodoform, sulphonal, and chloretone.
10.4.8 Uses of Formaldehyde
The 40% solution of formaldehyde (formalin) is used as disinfectant, germicide, and antiseptic. It is used for the preservation of biological specimens. It is used in making synthetic plastics, like bakelite, urea-formaldehyde resin, etc. Many carbonyl compounds are well known for their odour and flavours.
Carbonyl compounds, like vanillin (from vanilla beans), salicylaldehyde (from meadow sweet), and cinnamaldehyde (from cinnamon) have very pleasant fragrances. They are also used to manufacture solvents like acetone and for preparing materials like adhesives, resins, paints, perfumes, plastics, fibres, etc. Vanillin is 4-hydroxy-3-methoxybenzene carbaldehyde.
TEST YOURSELF
1. In Clemmensen reduction, carbonyl compounds are treated with (1) zinc amalgam +HCl
(2) sodium amalgam +HCl
(3) zinc amalgam + nitric acid
(4) sodium amalgam +HNO3
2. The increasing order of the rate of HCN addition to compounds I to IV is I) HCHO II) CH3COCH3 III) PhCOCH3 IV) PhCOPh (1) III<IV<II<I (2) I<II<III<IV (3) IV<II<III<I (4) IV<III<II<I
3. A, CH3 H 1. CH3MgBr 2. H3O+ C O
Here, compound A will be (1) 1° alcohol (2) 2° alcohol (3) 3° alcohol (4) 4° alcohol
4. Carbonyl compounds readily undergo (1) nucleophilic substitutions (2) electrophilic addition reactions (3) nucleophilic addition reactions (4) elimination reactions
5. Acetone is treated with excess of ethanol in the presence of HCl gas. The product obtained is
(1) (CH3)2 C OH OC2H5
(2) (CH3)2 C OC2H5 OC2H5
(3) CH3CH2CH2 CH3 C O
(4) CH3CH2CH2 CH2CH2CH3 C O
6. Acetone adds up which of the following without the elimination of water molecule? (1) NH2−OH (2) 2, 4 – DNP (3) H2N−NH2 (4) HCN
7. Which of the following does not undergo aldol condensation? (1) ClCH2CHO (2) CCl3−CHO (3) C6H5CH2HO (4) CH3CHO
8. 4 || NaBH 32 O CHCHCCHO → product(s) Product in the above reaction is (1) CH3CH2CH(OH)CH2OH (2) CH3CH2COOH+CO2 (3) CH3CH2COCH2OH (4) CH3CH2CH(OH)CHO
9. Which one of the following does not form addition product with NaHSO 3 solution? (1) HCHO (2) C6H5COCH3 (3) C6H5CHO (4) CH3CHO
10. Which of the following can give a positive test with 2, 4-D.N.P and negative test with Tollen’s reagent, and can also react with NaOI to give a yellow precipitate?
(1) CH3-CHO
(2) CH3−CH2−CO−CH2−CH3
(3) CH3−CH2−CO−CH3 (4) 33 CHCHCH | OH Answer Key
(1) 1 (2) 4 (3) 2 (3) 3 (5) 2 (6) 4 (7) 2 (8) 1 (9) 2 (10) 3
10.5 BENZALDEHYDE
Benzaldehyde is the simplest aromatic aldehyde which occurs in bitter almonds and it is also known as oil of bitter almonds.
10.5.1 Preparation
Chromyl chloride oxidises toluene to a chromium complex, which on hydrolysis, gives benzaldehyde. This reaction is called Etard reaction.
CH(OCrOHCl2)2 + CS2 CH 3
CrO 2 Cl 2
CHO H2O+ 3
Chromic oxide in acetic anhydride oxidises toluene or substituted toluene to benzylidene diacetate, which on hydrolysis with aqueous acid, gives benzaldehyde.
CrO 3 + CH 3 + (CH3CO)2O 1-10oC
CH(OCOCH3)2 CHO 3 HO + D →
Benzoyl chloride, on reduction with hydrogen in the presence of Lindlar’s catalyst (Rosenmund reduction), gives benzaldehyde. C C Cl H O O Pd BaSO4 +H2 +HCl
Side chain chlorination of toluene gives benzal chloride. Followed by hydrolysis, it gives benzaldehyde. This is a commercial method.
CH3 CHO CHCl2
Cl2, hν H2O , 100°C
When benzene is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous aluminium chloride or cuprous chloride, it gives benzaldehyde. This reaction is called Gattermann−Koch reaction.
CH3 CHO CHCl2
Cl2, hν H2O , 100°C
Gattermann aldehyde synthesis: Benzene is teated with a mixture of HCN and HCl in the presence of anhydrous AlCl 3 to form benzaldiminium tetrachloroaluminate (III), which is hydrolysed to produce benzaldehyde. This is also called Gattermann formulation.
+ HCN + HCl AlCl3
CH=NH + 2Cl– H2O CHO + NH4Cl + AlCl3
10.5.2 Properties of Benzaldehyde
Benzaldehyde undergoes addition reactions with hydrogen cyanide, sodium bisulphite, Grignard reagent, etc., just like acetaldehyde. Benzaldehyde undergoes condensation reactions with hydroxylamine, hydrazine, phenyl hydrazine, semicarbazide, etc., forming the corresponding condensation products.
Cannizzaro Reaction
Benzaldehyde undergoes self-oxidation reduction (disproportionation) reaction on treatment with concentrated alkali due to lack of hydrogen, forming benzyl alcohol and sodium benzoate.
Cross Aldol Condensation
Benzaldehyde undergoes cross condensation with a ketone in dilute alkali.
1,3-Diphen
Aromatic aldehydes and ketones undergo electrophilic substitution in which the carbonyl group acts as a ring deactivating and meta –directing
Perkin’s Reaction
An aromatic aldehyde, when heated with the anhydride of an aliphatic acid (containing two a–hydrogen atoms) and its sodium salt (base catalysed), condensation takes place and an a, b –unsaturated acid is formed. Benzaldehyde with acetic anhydride and sodium acetate yields cinnamic acid.
C6H5CHO + (CH3CO)2O 3 00 CHCOONa 170180C →
C6H5CH=CH–COOH
Tischenko Reaction
On heating benzaldehyde with aluminium ethoxide and a little of anhydrous AlCl3 or
ZnCl2, it undergoes intermolecular oxidation and reduction to produce benzyl benzoate.
Al(OC2H5 )3 C6H5C00CH2C6H5
5. An organic compound (X) with molecular formula C 8 H 8 O forms an orange red precipitate with 2, 4-DNP reagent and responds to iodoform test. It neither decolourises Baeyer’s reagent or bromine water and also it neither reduces Tollens’ reagent or Fehling’s reagent. Compound (X) gives a carboxylic acid (Y) with molecular formula C 7 H 6O 2 on drastic oxidation with chromic acid. Give the equations.
TEST YOURSELF
1. Select the incorrect one for the final product (P) in Etard’s reaction.
(1) P : Aromatic carbonyl compound
(2) P : Gives silver mirror with Tollen’s reagent
(3) P : Can participate in Cannizaro reaction
(4) P : Gives brick red ppt with Fehling’s solution
2. Example of electrophilic aromatic substitution reaction is (1) CO.HCl
Anthyd AlCl3 CuCl
(2) CrO2Cl2 CH3 CS2 H3O+ + (3) C Cl H2 Pd - BaSO4 O
Con HI OCH3
(4)
3. 2 v HO 32 h PhCH2ClA? −+→→
(1) Ph-CHO (2) Ph-COOH
(3) Ph-CH2-OH (4) Ph-COCl
4. Oxidation of toluene to benzaldehyde can be easily carried out with which of the following reagents?
Try yourself:
5. An organic compound (A) with molecular formula C 8 H 8 O forms an orange-red precipitate with 2, 4-DNP reagent and gives yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens’ nor Fehlings’ reagent. What is the compound A?
Ans: ‘A’ is acetophenone
(1) CrO3/acetic acid, H3O+
(2) CrO3/acetic anhydride, H3O+
(3) KMnO4/HCl, H3O+
(4) CO/HCl, anhydrousAlCl3
5. The reagent used for the separation of acetaldehyde from acetophenone is (1) NH2OH (2) NaHSO3
(3) NaOH/I2 (4) C6H5NHNH2
6. The product formed by the reaction of an aldehyde with a primary amine is (1) carboxylic acid (2) aromatic acid (3) Schiff’s base (4) ketone
7. The product formed in Gattermann−Koch benzal chloride reaction from benzene is (1) chlorobenzene (2) benzal chlordie (3) benzaldehyde (4) acetophenone
8. An aldehyde which undergoes Cannizzaro’s reaction and reduces Schiff’s reagent but does not reduce Fehling’s solution is (1) CH3CHO (2) HCHO (3) C6H5CHO (4) salicylaldehyde
9. Which of the following compounds does not react with NaHSO3?
(1) HCHO (2) C6H5COCH3 (3) CH3COCH3 (4) CH3CHO
10. Toulene, when heated with alkaline KMnO4 followed by acidification, gives ‘A’. A, on decarboxylation, gives B. B, in the presence of CO + HCl / CuCl, gives C. The reaction B→C is
(1) Gattermann−Koch reaction (2) Stephen’s reaction (3) MPV reduction (4) Etard reaction
11. Which of the following compounds gives a positive Tollen’s test but negative Fehling test?
(1) Acetaldehyde (2) Benzaldehyde (3) Acetophenone (4) Acetone
Answer Key
(1) 4 (2) 1 (3) 1 (4) 2
(5) 2 (6) 3 (7) 3 (8) 3
(9) 2 (10) 1 (11) 2
10.6 NOMENCLATURE AND STRUCTURE OF CARBOXYLIC GROUP
Carbon compounds which possess a carboxyl functional group, COH || O are called carboxylic acids. Higher members of aliphatic mono-carboxylic acids occur in fats as esters of glycerol. Hence, they are called fatty acids. The general formula of aliphatic carboxylic acids is C nH2nO2, represented by RCOOH.
The common names of acids are derived from the source of that particular acid. HCOOH is named formic acid as it is obtained from red ants (formica means red ant). CH3COOH is named acetic acid as it is present in vinegar (acetum means vinegar). CH3CH2CH2COOH is named butyric acid as it is present in rancid butter. CH3(CH2)3COOH, valeric acid, is present in the root of valerian plant.
In common system, the acids, except formic acid, are named derivatives of acetic acid. Example: CH3CH2COOH is methyl acetic acid, (CH3)3C–COOH is trimethyl acetic acid, etc.
In IUPAC system, the secondary suffix –oic acid is included after an appropriate root word and primary suffix. Systematic name of a saturated carboxylic acid is alkanoic acid. The names are listed in Table 10.3 and Table 10.4.
32 3 CHCHCHCHCOOH 54|3|21 CHCl g δba is called b –chloro– g –methyl valeric acid. Its IUPAC name is 3–chloro–4–methylpentanoic acid.
Table 10.3 Aliphatic carboxylic acids
HCOOH
CH3COOH
CH3CH2COOH
CH3CH2CH2COOH
Formic acid Methanoic acid
Acetic acid
Ethanoic acid
Propionic acid Propanoic acid
Butyric acid Butanoic acid
(CH3)2CHCOOH Isobutyric acid
HOOC–COOH
Oxalic acid Ethandioic acid
HOOC–CH2–COOH Malonic acid
HOOC(CH2)2COOH
HOOC(CH2)3COOH
HOOC(CH2)4COOH
HOOC–CH2–CH(COOH)–CH2 COOH
Propandioic acid
Succinic acid Butandioic acid
Glutaric acid
Adipic acid
Pentandioic acid
Hexandioic acid
Table 10.4 Aromatic carboxylic acids
Formula
Common name
IUPAC name
COOH
Benzoic acid
Benzenecarboxylic acid (Benzoic acid) C
10.6.1 Isomerism
Carboxylic acids may exhibit chain isomerism. T hey do not have metamers. Esters are functional isomers of carboxylic acids.
CH3COOH is isomeric with methyl formate, HCOOCH3.
Functional isomers of C 2 H 5 COOH are CH3COOCH3 and HCOOC2H5
6. What are the functional isomers of propanoic acid?
Sol. Functional isomers of carboxylic acids are esters, hydroxy aldehydes, hydroxy ketones and hydroxy oxiranes.
Propanoic acid can have the following functional isomers
■ Esters are HCOOC2H5, CH3COOCH3
■ Hydroxy aldehyde, CHO–CH 2CH2–OH
■ Hydroxy ketone, 32 O || CHCCHOH
■ Hydroxy oxiranes, 22 CHCHCHOH \O /
Try yourself:
6. How many functional isomers can acetic acid have?
Ans: Three
10.6.2 Acidic Nature
Carboxylic acids ionise in water and release H ⊕ forming a carboxylate ion which is its conjugate base. Proton is accepted by water in aqueous solutions of acid.
Applying law of mass action, the equilibrium constant is given as,
RCOOHO
K eq = 3 2
RCOOHHO
As water is in large excess and its concentration does not change much, the equilibrium constant is written as,
K a = 3
RCOOHO RCOOH
K a is acid dissociation constant. As the value of K a increases, the strength of the acid also increases.
The negative value of logarithm of K a is denoted as pKa; pKa = –log Ka. As the value of pKa decreases, strength of acid increases. So strength of a carboxylic acid increases with increase in K a and decreases with increase in pKa.
Carboxylic acids are stronger in acidic character than alcohols and phenols. Unlike phenols, carboxylic acids react with weaker bases such as carbonates and bicarbonates to liberate carbon dioxide gas. This reaction is useful in detecting the presence of carboxyl group in an organic compound.
2RCOOH + 2Na→ 2RCOONa + H 2
RCOOH + NaOH → RCOONa + H 2O
2RCOOH+Na2CO3→2RCOONa +H2O+CO2
RCOOH+NaHCO3→RCOONa+H2O+CO2
It is a reversible reaction and equilibrium is established. The carboxylate anion, RCOO– is stabilised by resonance:
The pKa value of hydrochloric acid is – 7.0, benzoic acid is 4.19, acetic acid is 4.76, and that of trifluoroacetic acid (CF 3COOH) (the strongest organic acid) is 0.23. Strong acids have pKa values less than 1, moderately strong acids have between 1 and 5. The pKa values of weak acids lie in between 5 and 15 and extremely weak acids have greater than 15.
Though the conjugate base of phenol, phenoxide ion has resonance structures, they are non-equivalent and that too in which the negative charge is present on the less electronegative carbon atom. In the resonance structures of carboxylate ion, the negative charge is present on more electronegative oxygen and that too, the two resonance structures are equivalent. Hence, the resonance in carboxylate ion is more important than in phenoxide ion, so carboxylic acids are more acidic than phenols.
Effect of substituent on the strength of acids: The strength of an acid depends on the stability of its conjugate base RCOO –Greater the stability of the conjugate base, stronger is the acid. Stability of the conjugate base depends on spreading of charge. Greater the charge spreading, more is the stability and less is the strength of the conjugate base. Correspondingly, the parent acid becomes stronger acid.
Charge spreading can take place by resonance or inductive effect. Groups with –I or –M effects increase the strength of an acid and +I or +M effects decrease the acidic strength. Presence of electron withdrawing groups increases the strength of the acid and electron releasing groups decreases the strength of the acid by de-establishing the conjugate base.
The effect of the following groups in increasing acidity order is :
C6H5 < I < Br < Cl < F < CN < NO 2 < CF3
The K a values of important carboxylic acids are listed in Table 10.5.
Table 10.5 The K a values of important carboxylic acids
(CH3)3CCOOH 8.91 × 10–6
C6H5COOH 6.35 × 10–5
C6H4 4.21 × 10–5
NCCH2COOH 3.65 × 10–3
FCH2COOH 2.57 × 10–3
ClCH2COOH 1.36 × 10–3
Cl2CHCOOH 5.33 × 10–2
Cl3CCOOH 2.32 × 10–1
HOOC–COOH 5.4 × 10–2
COOH
CH2 1.7 × 10–3
COOH
Based on the K a values, the following is the decreasing acidity order :
CF3COOH > CCl3 COOH > CHCl2COOH
> O 2 NCH 2 COOH > NCCH 2 COOH > FCH2COOH > ClCH2COOH > BrCH2COOH > HCOOH > ClCH2CH2COOH > C6H5COOH
> C 6 H 5 CH 2 COOH > CH 3 COOH > CH3CH2COOH
The –NO 2 group increases strength by exerting –M and –I effects and the –OCH 3 group decreases strength by exerting +M effect.
HCOOH > C6H5COOH > CH3COOH >
O2NCOOH > COOH >
H3COCOOH
When groups such as phenyl or vinyl are directly attached to the carboxylic acid, its acidic character is increased, contrary to expected decrease due to resonance as shown
This is due to greater electronegativity of sp 2 hybridised carbon to which carboxyl carbon is attached.
Acidic strength due to –I effect depends on positions : a−>b−>g−
CH 3 CH 2 CH(Cl)–COOH > CH 3 CH(Cl) CH2–COOH > (Cl)CH2CH2CH2–COOH
Acidic strength due to –I effect also depends on the nature of the group.
NO2–CH2COOH > CN–CH2COOH > OH – CH2COOH
–M effect is more pronounced at para position as compared to that at meta position.
Try yourself:
7. Among the compounds, acetic acid, ethylalcohol, water, acetylene and ethane, how many can react with sodium metal?
Ans: Four
TEST YOURSELF
1. Propionic acid can also be named
(1) methyl methanoic acid
(2) methyl acetic acid
(3) methyl ethanoic acid
(4) ethyl acetic acid
2. Which of the following compounds does not have a carboxyl group?
(1) Methanoic acid (2) Ethanoic acid
(3) Picric acid (4) Benzoic acid
3. Which of the following is a pair of functional isomers?
(1) CH3COCH3, CH3CHO
(2) C2H5CO2H, CH3CO2CH3
(3) C2H5CO2H, CH3CO2C2H5
(4) CH3CO2H, CH3CHO
4. IUPAC name of phthalic acid is (1) benzene-1, 4-dicarboxylic acid
The ortho-substituted isomer of every substituted benzoic acid (whether the substituent is electron releasing or electron withdrawing) is relatively stronger than the corresponding para and meta isomer. This is called ortho effect.
7. Among the compounds, phenol, acetylene, ethyl alcohol, formic acid, benzene sulphonic acid, and trinitrophenol, which compounds give effervescence upon addition with NaHCO3?
Sol Acids stronger than carbonic acid can react with NaHCO3 releasing CO2 gas, thus effervescence is observed. Such compounds among the given are formic acid, HCOOH, benzene sulphonic acid, C6H5–SO3H, trinitrophenol or picricacid.
(2) benzene-1, 2-dicarboxylic acid
(3) benzene-1, 3-dicarboxylic acid
(4) 2-Phenylethanoic acid
5. Number of structural isomers (carboxylic acids and esters) with the formula C 2H4O2 is/are
(1) 1 (2) 2
(3) 3 (4) 4
6. Vinegar is (1) 6 – 10% acetic acid
(2) 50% acetic acid
(3) 6 – 10% oxalic acid
(4) 75% valeric acid
Answer Key
(1) 2 (2) 3 (3) 2 (4) 2
(5) 2 (6) 1
10.7 PREPARATION OF CARBOXYLIC ACIDS
Carboxylic acids can be prepared from alcohols, esters, cyanides, etc., as follows.
10.7.1 From Primary Alcohols and Aldehydes
Carboxylic acids are prepared by the oxidation of primary alcohols or aldehydes, using acidic, alkaline or neutral potassium permanganate or potassium dichromate and chromium trioxide in acidic media.
RCH2OH 4227 24 KMnO(or)KCrO HSO → RCHO
4227 24 KMnO(or)KCrO HSO → RCOOH
CH3CH2OH 4227 24 KMnO(or)KCrO HSO → CH3CHO
4227 24 KMnO(or)KCrO HSO → CH3COOH
CH3(CH2)6CH2OH 3 24 CrO HSO → 1- Octanol
CH3(CH2)6COOH
Octanoic acid
CH3(CH2)8COOH 3 24 CrO HSO → 1- Decanol CH3(CH2)8COOH Decanoic acid
Strong oxidising agent: Hot KMnO4, Hot K2Cr2O7, Conc. KMnO4, Conc.K2Cr2O7, Acidified KMnO4, Acidified K2Cr2O7,
Oxidation of alcohol by strong oxidising agent: CrO3/H+
10.7.2 From Grignard Reagents
Grignard reagents combine with carbon dioxide (dry ice) and form a salt. The salt gives a carboxylic acid on hydrolysis.
RMgX + CO2 Dry ether → R–COO–MgX
2 HO H + → RCOOH + Mg(OH)X
CH3MgBr + CO2→ CH3COOMgBr
3 HO + → CH3COOH + Mg(OH)Br
The acid formed has one carbon atom more than the alkyl group present in the Grignard reagent ascending the series.
10.7.3 From Cyanides, Esters, and Amides
Alkyl and aryl nitriles on acid or alkaline hydrolysis give amides, which on further hydrolysis, give carboxylic acids.
RC ≡ N 2 HO HorOH + → RCONH2 2 HO H(or)OH+− →
RCOOH+NH3
This method serves as a very good synthetic method for the preparation of carboxylic acids.
CH3CN 2 HorOH HO +− → CH3CONH2 +−
D → HorOH CH3COOH+NH3
Esters also give carboxylic acids on hydrolysis in the presence of dilute mineral acids.
RCOOR' + H2O RCOOH + R'OH
CH 3 COOC 2 H 5 2 HO,H + → ← CH 3 COOH+ C2H5OH
During base hydrolysis, carboxylates are formed, which on acidification, give corresponding caboxylic acids.
R R R R (O) (O)
OH no reaction C R R R OH (O) no reaction
CH3CH2COOC2H5 NaOH → ←
CH3CH2COONa 3 HO + → ←
CH3CH2COOH
Acidic hydrolysis of esters gives directly carboxylic acids.
COOC2H5
3 HO + COOH + C2H5OH
This method is particularly useful for the preparation of higher fatty acids from oils and fats, which are triesters of glycerol.
C6H5COOC2H5 2 HO,H + → ←
C6H5COOH+C2H5OH
C6H5CH2OH HBr → C6H5CH2Br KCN →
C6H5CH2CN 2 HO,H + D → C6H5CH2COOH
CH3CONH2
CONH2
3 HO + D → CH3COOH+ NH3
3 HO + D → COOH +NH3
10.7.4 From Alkylbenzene
Aromatic carboxylic acids can be prepared by oxidation with chromic acid (or) acidic (or) alkaline KMnO 4. The entire side chain is oxidised to the carboxyl group irrespective of length of the side chain. Primary and secondary alkyl groups are oxidised in this manner while tertiary group is not affected. CH3
10.7.5 From Acyl Halides and Anhydrides
Acid chlorides on hydrolysis with water or base hdrolysis followed by acidification and anhydrides on hydrolysis with water, carboxylic acids are formed.
RCOCl 2 HO → RCOOH + HCl 2 + 3 HO OH HO RCOClRCOOCl | RCOOH →+
(C6H5CO)2O 2 HO → 2C6H5COOH
C6H5COOCH3 2 HO →
C6H5COOH+CH3COOH
10.7.6 Acetic Acid Is Prepared by the Following Methods
From methyl alcohol and carbon monoxide:
In the presence of rhodium or cobalt, methanol combines with carbon monoxide and forms acetic acid.
CH3OH + CO Co/Rh ,Pressure D → CH3COOH
From acetaldehyde:
Acetic acid is commercially prepared by the oxidation of acetaldehyde with air in the presence of manganese acetate catalyst.
CH3CHO+ 1 2 O2 32 air Mn(OCOCH) → CH3COOH
From ethyl alcohol:
Vinegar is 6–10% aqueous solution of acetic acid. It is obtained by fermentation of liquors containing 12 to 15% ethyl alcohol. Fermentation is done by bacterium Mycoderma aceti in the presence of air at 30–35°C. This process is termed acetous fermentation.
CH3CH2OH + O2→ CH3COOH + H2O
8. When a compound A of the formula C2H5Br reacts with magnesium in the presence of ether to form Grignard reagent which upon reaction with dry ice followed by acidification, is converted into a carboxylic acid, B. Two moles of B can also be given by one mole of C
10: Aldehydes, Ketones and Carboxylic Acids
upon its ozonolysis. Identify the compounds, A, B and C.
Ozonolysis of an Alkyne can produce carboxylic acid
Therefore, A is Ethylbromide, B is propanoic acid and C is 3–hexyne.
Try yourself:
8. When a alkyl halide of formula, CH 3 Br is converted into Grignard reagent by treating it with magnesium in ether and finally made to react with dry ice followed by acidification, a carboxylic acid, A is formed. Two moles of A is formed upon ozonolysis of an alkyne, B. What is the systematic name of the B?
Ans: Butyne-2
TEST YOURSELF
1. Identify ‘C’ in the following sequence of reactions
(1) CH3CH2CONH2
(2) CH3CN
(3) (CH3CO)2O
(4) CH3COOH
2. 1-butyne on oxidation with hot alkaline KMnO4 would yield which of the following as end product?
(1) CH3CH2CH2COOH
(2) CH3CH2COOH
(3) CH3CH2COOH+CO2+H2O
(4) CH3CH2COOH+HCOOH
3.
The product ‘B’ is (1) acetic acid (2) acetone (3) acetaldehyde (4) formic acid
4. Which one of the following reactions will not yield propionic acid?
(1) CH3CH2CCl3+OH /H3O+
(2) CH3CH2COCH3+IO/H3O+
(3) CH3CH2CH2OH+KMnO4/H+
(4) CH3CH2CH2Br+Mg, CO2 dry ether/H+
5. Which one of the following functional groups undergoes hydrolysis with alkali to yield an acid group?
(1) -CN (2) -CHO
(3) -COCH3 (4) -Br
6. Oxidation of primary alcohols finally gives (1) aldehydes (2) ketones (3) carboxylic acids (4) esters
7. In the reaction, Ethanol PI33HO KCN ABC; + D →→→ here C is (1) acetamide (2) propionamide (3) propanoic acid (4) acetic acid
8. () 2 2 ClOnemoleRedP 3 HO/H alc.KCN CHCOOH X YZ; + → → → (1) Lactic acid
(2) Propionic acid (3) Malonic acid (4) Fumaric acid
9. Hydrolysis of acetamide produces (1) acetic acid
(2) acetaldehyde (3) methyl amine
(4) formic acid
10. Z in the following sequence is 3 3 CHCl Zn dust anhyd.AlCl 4 Alkaline Phenol X YZ. KMnO →→
(1) Toluene (2) Benzene (3) Benzoic acid (4) Benzaldehyde
Answer Key
(1) 4 (2) 3 (3) 1 (4) 4
(5) 1 (6) 3 (7) 3 (8) 3
(9) 1 (10) 3
10.8 PROPERTIES OF CARBOXYLIC ACIDS
Carboxylic acids are stronger acids than alcohols and phenol. In their properties –COOH group is involved.
10.8.1 Physical Properties
Aliphatic carboxylic acids up to nine carbon atoms are colourless liquids at room temperature with unpleasant odour.
The higher acids are wax like solids. Carboxylic acids are higher boiling liquids than aldehydes, ketones, alkyl halides, ethers, alkanes and even alcohols of comparable molecular masses. This is due to more extensive association of carboxylic acid molecules through intermolecular hydrogen bonding. Even in vapour state, the hydrogen bonds are not broken completely. In liquid state, carboxylic acids are polymeric. In the vapour state or in non-aqueous solutions, they are dimeric.
and miscible with water in all proportions. 100% acetic acid free of water is called glacial acetic acid. Since the mp of anhydrous acetic acid is 17 0C, it is solid in a refrigerator and looks “icy”, hence the name.
Structure of Carboxyl Group
In carboxylic acids, the bonds to the carboxyl carbon lie in one plane and are separated by about 120 0 . The carboxylic carbon is less electrophilic than carbonyl carbon because of the possible resonance structure shown below:
10.8.2 Chemical Properties
In chemical reaction of Carboxylic acids, O–H bond, C–O bond and C–C bond of the acids are involved.
Reactions Due to the Fission of O–H Bond
Carboxylic acids release hydrogen with active metals like sodium. Similar to phenols.
2RCOOH + 2Na→ 2RCOONa + H 2↑
2CH3COOH + 2Na→CH3COONa + H2↑
Carboxylic acids form salts with alkalies like sodium hydroxide, calcium hydroxide, etc.
Carboxylic acids up to four carbon atoms are highly soluble in water due to the formation of hydrogen bonds with water. Solubility of acid decreases with an increase in the size of hydro-phobic alkyl group. Carboxylic acids are also soluble in less polar organic solvents like benzene, chloroform, ether, etc. The simplest aromatic carboxylic acid, benzoic acid is nearly insoluble in cold water.
RCOOH + NaOH→RCOONa + H 2O
CH3COOH + NaOH→CH3COONa + H2O
2CH3COOH + Ca(OH)2 →
(CH3COO)2Ca + 2H2O
Unlike phenols, carboxylic acids react with weaker bases like carbonates and bicarbonates to evolve carbon dioxide. This reaction is used to detect the presence of carboxyl group in an organic compound.
2RCOOH + Na2CO3→
Acetic acid is a colourless pungent liquid with a boiling point of 118°C. It is sour to taste
2RCOONa + H2O + CO2↑
10: Aldehydes, Ketones and Carboxylic Acids
2CH3COOH + Na2CO3→
2CH3COONa + H2O + CO2↑
RCOOH + NaHCO3 →
RCOONa + H 2O + CO2↑
CH3COOH + NaHCO3 →
CH3COONa + H2O + CO2↑
Acids stronger than carbonic acid release carbon dioxide from carbonates or bicarbonates. This reaction is characteristic of carboxylic acids and they can be distinguished from other compounds. Carboxylic acids can be separated from other compounds by dissolving in NaHCO3 or Na2CO3. The sodium salt of acid formed regenerates acid on adding HCl.
Reactions Due to the Fission of C–O Bond
Formation of esters: Carboxylic acids react with alcohols and phenols in the presence of conc. H2SO4 or HCl gas catalyst and form esters. This is called Fischer’s esterification. It is a reversible reaction. Esters have pleasant fruity smell.
RCOOH + HOR HSO24
CH3COOH + HOC2H5
Mechanism:
R–COOR + H2O
CH3COOC2H5 + H2O
Formation of Anhydrides
On heating with a dehydrating agent like phosphorus pentoxide, carboxylic acids form acid anhydrides.
2RCOOH 25 2 PO HO → RCOOCOR + H2O
2CH3COOH 25 2 PO HO → CH3COOCOCH3 + H 2O
Formation of Acid Chlorides
Carboxylic acids form acid chlorides with thionyl chloride or phosphorus pentachloride or phosphorus trichloride. Thionyl chloride is the preferred reagent.
CH3COOH + PCl5→ CH3COCl + POCl3 + HCl
3CH3COOH + PCl3→3CH3COCl + H3PO3
CH3COOH +SOCl2→CH3COCl + SO2 + HCl
Reaction with NH3
When heated with ammonia, carboxylic acids form amides.
RCOOH + NH3 → ← 4 RCOONH + D → RCONH2 + H2O COOH COOH +2NH3 → ← COO
CH3COOH + NH3 → ← CH3CONH2 + H2O
Reactions Involving –COOH Group
Reduction: On reduction with lithium aluminium hydride or diborane, carboxylic acids form primary alcohols. Sodium borohydride does not reduce the carboxyl group.
RCOOH 426 3 1)LiAlH|etherorBH 2)HO + → RCH2OH
CH3COOH 4 LiAH → l CH3CH2OH
Oxidation: Acetic acid is highly resistant to oxidation, but on prolonged heating with oxidising agents finally produces carbon dioxide and water.
Reactions Involving Alkyl Group of Acid
In reactions of salts of carboxylic acids, many bond rearrangements are possible,
The a –hydrogens of a carboxylic acid are substituted by chlorine or bromine atoms when the acid reacts with Cl 2 or Br 2 in the presence of red phosphorus. This reaction is called Hell–Volhard–Zelinsky (HVZ) reaction. In this reaction, a -halocarboxylic acids are formed.
RCH2COOH + Cl2 2 (i)redP (ii)HO →
RCH(Cl)COOH + HCl
Acetic acid reacts with chlorine in the presence of red phosphorus to give monochloro-, dichloro- and trichloro acetic acid.
CH3COOH + Cl2 redP → ClCH2COOH + HCl
CH2ClCOOH +Cl2 redP → CHCl2COOH + HCl
CHCl2COOH + Cl2 redP → CCl3COOH + HCl
Reaction of Salts of Acid
Salts of carboxylic acids undergo the following reactions
Decarboxylation
Carboxylic acids undergo decarboxylation when their sodium salts are heated with soda lime, and form hydrocarbons. The hydrocarbon formed will have one carbon less than the acid from which it is formed.
RCOO–Na+ + NaOH CaO D → RH + Na2CO3
CH3COO–Na++NaOH CaO D → CH4+Na2CO3
C6H5COO–Na++NaOH CaO D → C6H6+ Na2CO3
Kolbe’s Electrolysis
When the aqueous solution of sodium salt of an acid is subjected to electrolysis, a hydrocarbon having twice the number of carbon atoms present in the alkyl group of the acid is formed. In Kolbe’s reaction, we also get alkane and alkene as disproportionation product.
RR+2CO+2NaOH+H
2RCOO–Na++2H2O Electrolysis → 22 anodecathode
2CH3COONa + 2H2O Electrolysis →
CH3–CH3 + 2CO2 + 2NaOH + H2
Ring Substitution
Aromatic carboxylic acids undergo electrophilic substitution reactions. Carboxyl group is meta directing and deactivating. Aromatic carboxylic acids, however, do not undergo Friedel-Crafts reaction because the carboxyl group is strongly deactivating in nature. Hence nucleophilicity of benzene ring decreases.
With nitration mixture, benzoic acid forms m-nitrobenzoic acid. NO2
COOHCOO 3H 24 conc.HNO conc.HSO →
With chlorine, in the presence of ferric chloride, benzoic acid forms m-chloro benzoic acid as main product. Cl
COOHCOO 2H 3 C FeCl → l
Hunsdiecker Reaction
Bromo alkanes can be easily prepared by refluxing the silver salt of fatty acid with bromine in carbon tetrachloride.
CH3CH2COOAg + Br2 4 CCl/Reflux →
CH3CH2Br + CO2 + AgBr
This reaction undergoes free radical mechanism. The yield of the alkyl halide is primary > secondary > tertiary.
With I2, silver salts give esters instead of iodo alkanes. Reaction is known as BirnBaumSimonini reaction.
2RCOOAg + I2 4 CCl/ D →
RCOOR + 2AgI + CO 2
10.8.3 Uses
■ Acetic acid is used as a solvent.
■ About 6–10% acetic acid is used as vinegar in cooking.
■ Formic acid is used in rubber, textile, dyeing, leather and electroplating.
■ Hexanedioic acid is used in the manufacture of nylon–6, 6, a polymer.
■ Esters of benzoic acid are used in the preparation of perfumes.
■ Sodium benzoate is used as food preservative.
■ Higher fatty acids are used for the manufacture of soaps and detergents.
9. A carboxylic acid has the formula, C4H6O2. Its structural isomer is formed when another carboxylic acid X reacts with enthylalcohol in the presence of a few drops of conc. H2SO4 What is the compound, X?
Sol. Since, the acid, x reacts with C2H5OH to give the compound of the formula, C4H8O2, the x must have two carbon atoms. Therefore, the carboxylic acid is Acetic acid, CH 3COOH.
Try yourself:
9. A carboxylic acid of the formula, C2H4O2(A) upon reduction with LiAlH 4 and an acid gives the compound, C2H 6O(B) when the compounds A and B react with each other a product, C is formed. The structurel of C has one primary alcoholic group and one isomer keto group. What is the systematic name of C?
Ans: 3-hydroxybutan-2-one
TEST YOURSELF
1. pka is least for
(1) BrCH2CH2COOH
(2) C6H5COOH
(3) HCOOH
(4) ClCH2−COOH
2. Propanoic acid is slightly weaker than acetic acid because (1) methyl group is electron with drawing (2) +I effect of C2H5 is more than –CH3
(3) the methyl group in acetic acid shows hyperconjugation.
(4) propanoic acid has two α-hydrogens.
3. Consider the following transformations ()() 2 O I 33 PCCNaOH CHCHOHCHAB →→
The molecular formula of B is (1) CH3–C(OH)(I)CH3 (2) ICH2–COCH3
(3) CHI3
(4) CH3l
4. The correct decreasing order of acidity of the following is
I) HCOOH II) CH3COOH
III) CH3CH2COOH IV) C6H5COOH
(1) (I)>(II)>(III)>(IV)
(2) (IV)>(I)>(II)>(III)
(3) (I)>(IV)>(II)>(III) (4) (IV)>(I)>(III)>(II)
5. In the reaction, CH 3 COOH 5 4 PCl LiAlH AlC. KOH ABC →→→ , the product C is (1) ethylene (2) acetyl chloride
(3) acetaldehyde (4) acetylene
6. Which of the following will not undergo Hell–Volhard Zelinsky (HVZ) reaction?
(1) CH3COOH
(2) (CH3)2CH−COOH
(3) CHCl2-COOH
(4) HCOOH
7. 4 LiAlH 3 CHCHCHCOOH−=−→ X. The product X is (1) CH3CH2CH2CH2OH (2) CH3CH=CHCH2OH (3) CH3CH=CHCHO (4) CH3CH2CH2CHO
8. Acetic acid is treated with metallic sodium to form x and hydrogen. When X is treated with sodalime, Y and sodium carbonate are formed. ‘Y’ is (1) C2H6 (2) CH4 (3) CH3COONa (4) CH3CONH2
9. During Kolbe’s electrolysis of potassium acetate solution the anode products are, respectively,
CHAPTER REVIEW
Nomenclature and Structure of Carbonyl Group
■ Aldehydes and ketones contain the carbonyl functional group.
■ According to IUPAC nomenclature, aldehydes are called alkanals and ketones are called alkanones.
■ Ketones having five or more carbon atoms exhibit metamerism.
Preparation of Aldehydes and Ketones
■ Primary alcohols on oxidation or on catalytic dehydrogenation give aldehydes and secondary alcohols on similar conditions yield ketones.
■ Dry distillation of calcium salts of fatty acids, along with calcium formate, give aldehydes.
■ Symmetrical ketones may be obtained when calcium salts of fatty acids alone are heated.
■ Vapours of fatty acids mixed with formic acid when passed over heated thoria or alumina or MnO give aldehydes.
(1) CH3−CH3, CO2
(2) CH3−CH3, H2
(3) CH3−CH2−CH2−CH3, CO2
(4) CH4, CH3−CH3
10. Which of the following carboxylic acids undergoes decarboxylation easily?
(1) C6H5-CO-CH2-COOH
(2) C6H5-CO-COOH
(3) 65 | OH CHCHCOOH
(4) 2 65 | NH CHCHCOOH
Answer Key
(1) 4 (2) 2 (3) 3 (4) 3 (5) 1 (6) 4 (7) 2 (8) 2 (9) 1 (10) 1
■ Vapours of a fatty acid alone give ketone on treating with Al2O3 or MnO.
■ Alkenes can be oxidised to carbonyl compounds by Wacker process by using aqueous palladium chloride in the presence of cupric chloride catalyst.
■ Depending upon the structure of alkene, different carbonyl compounds are obtained by the reductive ozonolysis.
■ Carbonyls are obtained by the hydration of alkynes or by alkaline hydrolysis of gem dihalides.
■ Reduction of acid chloride with hydrogen in the presence of Lindlar’s catalyst to give aldehydes is called Rosenmund reduction.
■ Ketones cannot be prepared by Rosenmund method.
Physical Properties
■ Carbonyl compounds are highly polar and boil at high temperatures than the weakly polar ethers of comparable molar masses.
■ Lower carbonyls are more soluble in water due to hydrogen bonding.
■ Due to larger size of hydrophobic alkyl group, higher c arbonyls are insoluble in water.
Chemical Reactions
■ The characteristic reactions of carbonyl compounds are nucleophilic addition reactions.
■ Aldehydes are more reactive than ketones. Aliphatic aldehydes are more reactive than aromatic aldehydes.
■ Ammonia reacts with aldehydes and ketones to form imines.
■ Carbonyl compounds condense with derivatives of ammonia, hydroxylamine, hydrazine, phenylhydrazine, 2, 4-dinitrophenyl hydrazine, semicarbazide to form the corresponding oximes, hydrazones, phenyl hydrazones, 2, 4–dinitrophenyl hydrazones and semicarbazones.
■ Carbonyl compounds react with PCl 5 or thionyl chloride to give gem dihalides.
■ Aldehydes are reduced to primary alcohols and ketones to secondary alcohols with LiAlH 4 , NaBH 4 or by catalytic hydrogenation.
■ Carbonyl group is reduced to methylene group, by Clemmensen or by WolffKishner reduction, thereby, carbonyl compounds are reduced to alkanes.
■ Aldehydes are easily oxidised to carboxylic acids by even mild oxidising agents like Tollen’s reagent, Fehling’s reagent and Benedict’s solution. These oxidation reactions are used to distinguish aldehydes from ketones.
■ The a–hydrogens in carbonyl compounds are acidic.
■ Carbonyl compounds having at least one a–hydrogen, undergo Aldol condensation.
■ Aldehydes with no a -hydrogen atom on reaction with concentrated alkali undergo Cannizzaro reaction in which aldehyde undergoes disproportionation to give alcohol and salt of carboxylic acid.
■ Compounds containing methyl keto group or which form these on treatment with halogens give haloform reaction.
Benzaldehyde
■ Aromatic carbonyl compounds undergo electrophilic substitution reactions.
■ Carbonyl group present in aromatic ring is meta directing and deactivating.
■ Benzaldehyde can be obtained by the oxidation of toluene with chromyl chloride followed by hydrolysis. This is called Etard reaction.
■ Benzaldehyde is also obtained from benzene by Gattermann–Koch reaction.
Nomenclature and Structure of Carboxylic Group
■ Carboxylic acids are compounds which contain –COOH group as functional group with general formula CnH2nO2 or C nH2n+1 COOH.
■ Trivial names are given based on source.
■ HCOOH is named formic acid because it is obtained by distillation of ants (Latin).
■ The IUPAC name of carboxylic acids is alkanoic acid.
■ Carboxylic acids release H+ ions in aqueous solution and so are acidic in nature
Preparation of Carboxylic Acids
■ Carboxylic acids are prepared by oxidation of primary alcohols and aldehydes.
■ Carboxylic acids are prepared by the action of CO2 on Grignard reagent followed by hydrolysis.
■ Carboxylic acids are prepared by the hydrolysis of alkyl cyanides and amides.
■ Methyl alcohol on treatment with CO in the presence of Co or Rh (catalyst) under high pressure and temperature gives acetic acid.
■ Acetic acid is commercially prepared by the oxidation of acetaldehyde by air in the presence of manganous acetate as catalyst
■ Acidic hydrolysis of esters gives directly carboxylic acids while basic hydrolysis gives carboxylates, which on acidification give the corresponding carboxylic acids.
■ Aromatic carboxylic acids are prepared by the oxidation of alkyl benzenes.
■ Acidified KMnO 4 or acidified K 2 Cr 2 O 7 oxidises alkenes to ketones and / or acids.
Properties of Carboxylic Acids
■ Carboxylic acids release H2 with Na, release CO2 with NaHCO3 or Na2CO3
■ Carboxylic acids dissolve in NaOH and are regenerated by HCl (not by CO 2).
■ Carboxylic acids form esters with alcohols, acid chlorides with PCl3, PCl5 or SOCl2 and amides with NH3.
■ On heating with Phosphorous pentoxide, Carboxylic acids give anhydrides, on reduction with LiAlH4, they give primary alcohols.
■ Carboxylic acids give aldehydes and ketones when their calcium salts are heated with calcium formate and alone respectively.
■ Decarboxylation of carboxylic acids gives hydrocarbons in the presence of soda lime.
■ Carboxylic acids with -hydrogen form -chloroacids with Cl2 in the presence of red phosphorus. This is called HVZ reaction.
■ A 6 to 10% dilute aqueous acetic acid is called vinegar. It is used in cooking.
■ Alcohols, phenols and carboxylic acids are acidic because they liberate hydrogen gas on reaction with sodium metal.
■ Alcohols have no reaction with NaOH but phenols and carboxylic acids react with NaOH. Thus alcohols are less acidic than phenols and carboxylic acids.
■ Phenols and carboxylic acids turn blue litmus to red litmus, alcohols cannot give this test.
■ Carboxylic acids decompose NaHCO3 and liberate CO2 gas.
■ Phenol cannot decompose NaHCO3. Thus phenols are less acidic than carboxylic acids.
■ Carboxylic acids are weaker than mineral acids. This can be proved from pKa values.
■ The substituents which stabilise the carboxylate ion will increase the acidic strength of carboxylic acids.
■ Electron withdrawing groups increase the acidic strength of carboxylic acids.
■ Electron donating groups decrease the acidic strength.
■ With increasing the electron withdrawing tendency of groups acidic strength increases.
■ Electron withdrawing tendency of some groups is,
CF3 > NO2 > CN > F > Cl > Br > I > C6H5
■ With increasing number of electron withdrawing substituents, acidic strength increases.
■ With increase in the distance of electron withdrawing group from -COOH, acidic strength decreases.
■ Alkyl substituents have electrons donating nature. With increasing the number of carbon atoms in alkyl substituent electron donating tendency increases and acidic strength decreases.
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
■ Direct attachment of C6H5-, CH2=CH- to carboxylic acids increases the acidity, due to greater electronegativity of sp 2 carbon, contrary to the decrease expected due to resonance effect.
■ In benzoic acid also electron withdrawing substituents increases the acidic strength but electron donating substituents like –CH3, –OH, –NH2, etc decreases the acidic strength.
■ The ortho isomer of every substituted benzoic acid is stronger than benzoic acid. This is called ortho effect.
■ Among p- and m-isomers, p-isomer has more acidic character than m-isomer for electron with drawing group.
■ The m-isomer is stronger acid than benzoic acid while p-isomer is weaker than benzoic acid for electron releasing group.
Exercises
JEE MAIN LEVEL
Level - I
Namenclature and Structure of Carbonyl Group
Single Option Correct MCQs
1. Re garding Cinnamaldehyde the incorrect statement is
(1) 3 – phenyl – prop – 2 – enal is its IUPAC name
(2) It can exhibit geometric isomerism
(3) Number of π bonds present in one molecule are equal to five
(4) It is b,g - unsaturated aldehyde
2. The correct IUPAC name of valeraldehyde
(1) Propanal
(2) 2- methyl propanal
(3) Pentanal
(4) Cyclobutane carbaldehyde
3. What is the common name of 4-hydroxy3-methoxy benzaldehyde?
(1) Vanillin
(2) Acetophenone
(3) Butyraldehyde
(4) Benzaldehyde
4. Wrong match in the following structure IUPAC name
(1)
Benzene –1, 2 – dial
(2)
3 – bromo bezene carbaldehyde
(3) CH2 = CHCHO Prop – 2 – enal
(4) 2 – methyl cyclo hexanone
5. What is the common name of 2 -propanone?
(1) Acteone
(2) Acetophenone
(3) Butyraldehyde
(4) Benzaldehyde
6. The IUPAC name of methyl isopropyl ketone
(1) 3 – methyl – 2 – pentanone
(2) 3 – methyl butan – 2 - one
(3) 2 - pentanone
(4) 2 – methyl pentanone
7. cannot be called as
(1) Acetophenone
(2) Methyl phenyl ketone
(3) 1 – phenyl ethanone
(4) Benzophenone
8. What is the IUPAC name of Methyl phenyl ketone?
(1) 1-Phenylethan-1-one
(2) 1-Phenylpropan-1-one
(3) 1-Phenylethan-2-one
(4) 1-Phenylpropan-2-one
10. The IUPAC name of b-methylvalerladehyde
(1) 2- methyl pentanal
(2) 2-methyl butanal
(3) 3-methyl pentanal
(4) 3- methyl butanal
11. Pentan-2-one and Pentan-3-one are a pair of
(1) Chain isomers
(2) Metamers
(3) Positional isomers
(4) Tautomers
Preparation of Aldehydes and Ketones
Single Option Correct MCQs
12. Which of the following reagent is used for the following reaction ? ? 2 RRCHOHCHO −−→−
(1) Dry Distillation
(2) CCl4
(3) K2Cr2O7/H2SO4
(4) Heating with NaOH
13. An organic compound CH 3CH(OH)CH 3 on treatment with acidified K2Cr2O7 gives compound ‘Y’ which reacts with I 2 and sodium carbonate to form triiodo methane. The compund ‘Y’ is
(1) CH3OH
(2) CH3COCH3
(3) CH3CHO
(4) CH3CH(OH)CH3
14. When ethyl alcohol is passed over red hot copper at 300°C the formula of the product formed is
(1) CH3CHO (2) CH3COCH3 (3) C2H4 (4) CH3COOH
15. Which of the following compounds will give butanone on oxidation with PCC solution?
(1) Butan-1-ol (2) Butan-2-ol
(3) Propanol-1 (4) Propanol-2
16. Which one of the following reactions will not form acetal dehyde
(1) 324 / 32 CrOHSO CHCHOH → (2) 22 2 / 222 PdCu HO CHCHO ++ =+→
(3) 32 573 Cu K CHCHOH →
(4) 2 3 DIBALH HO CHCN →
17. Reagent used to convert ally alcohol to acrolein is
(1) KMnO4 (2) H2O2
(3) MnO2 (4) OsO4
18. In Oppenauer’s oxidation,
(1) secondary alcohol is oxidized to carboxylic acid in acetone solvent using aluminium tertiary butoxide
(2) secondary alcohol is oxidized to carboxylic acid without affecting the C = C bond by aluminium tertiary butoxide in acetone solvent
(3) secondary alcohol is oxidised to ketone without affecting C = C or bond by aluminium tertiary butoxide
(4) secondary alcohol is oxidized to ketone by chromic acid – pyridine complex
19. Dry Distillation of (CH3COO)2Ca gives
(1) CH3CHO
(2) CH3COOH
(3) CH3COCH3
(4) C2H5–O–C2H5
20. Compound formed when a mixture of vapours of formic and acetic acid is passed over ‘MnO’ at 300°C is
(1) Acetone
(2) Acetaldehyde
(3) Acetic anhydride
(4) Aldol
21. The product formed by the reaction of propyne with dil. H2SO4 in the presence of Hg2+ can not be prepared by the following reaction
(1) Dry distillation of calcium ethanoate
(2) By passing vapours of ethanoic acid over MnO at 300°C
(3) By ozonolysis of 2- Butene
(4) By alkaline hydrolysis of isopropylidene chloride
22. Which of the following reagents/ reactions will convert ‘A’ to ‘B’?
(1) PCC oxidation
(2) Ozonolysis
(3) BH 3 , H 2 O 2 / – OH followed by PCC oxidation
(4) HBr, hydrolysis followed by oxidation by K2Cr2O7
23. An alkene that provides only Butanone-2 on ozonolysis is
(1) 3, 4-dimethylhex-3-ene
(2) 2, 3-dimethylhex-2-ene
(3) 3-methylhex-3-ene
(4) 2, 3-dimethylpent-2-ene
24. The catalyst in Wacker process is
(1) CuCl2
(2) PdCl2
(3) Cu2Cl2
(4) Pd
25. The major product of the following reaction is ()2 2 AlHiBu HO RCN−≡→
(1) R-COOH
(2) RCONH2
(3) R-CHO
(4) R-CH2NH2
26. Ethylidene chloride (CH 3 CHCl 2 ) on hydrolysis with NaOH gives
(1) CH3CHO
(2) CH3COCH3
(3) CH3CH(OH)2 (4) CH3CH(OH)2
27. Rosenmund’s reduction is used for the preparation of (1) Carboxylic acid
(2) aldehydes
(3) Esters
(4) Carbohydrates
28. 33 CN CHCHCHO ≡→
Reagents useful for this conversion is / are
(1) I) SnCl2 + conc. HCl; II) H3O+
(2) I) DIBAL – H; II) H2O
(3) dil. H2SO4
(4) both (1) and (2)
29. The oxidation of toluene to benzaldehyde by chromyl chloride is called (1) Etard reaction
(2) Riemer –Tiemann reaction
(3) Wurtz reaction
(4) Cannizzaro’s reaction
30. Identify major product ‘X’ formed in the following reaction:
CO, HCl Anhydrous AlCl3/CuCl X (major product)
(1) (2)
(3) (4)
31.
The electrophile involved in the above reaction is
(1) Trichloromethyl anion () 3 CC
(2) Formyl cation CHO ⊕
(3) Dichloromethyl cation 2 CHC ⊕
(4) Dichlorocarbene () 2 : CC
32.
The product “P” in the above reaction is
34. In this reaction () 3 2 3 O 653 CHMCH65 CHCO alkaline CrOhydrolysis CH CHO →→ acetic anhydride is used
(1) As a catalyst
(2) As an oxidising agent
(3) To form a non–oxidizable derivative of benzaldehyde
(4) To help the reaction to proceed smoothly
35. In the following sequence of reactions : Toluene 22/HO/373 K AB Clhv →→ The product B is
(1) CH65COOH (2) CH653 CH
(3) CH652CHOH (4) CH65CHO
36. Determine the major product of the following reaction: () 3 32 2 2 dryether CHCOClCHCHCd−−+→
(1) CH 3COCH 2CH 3 + CH 3COCH 2 CH 3 + CdCl2
(1)
(2) (3)
(4)
33. The addition of Grignard reagent CH3MgBr to acetaldehyde is a nucleophilic addition reaction? The electrophile in this reaction is (1) CH3CHO (2) CH3+ (3) CH3– (4) Br–
(2) CH3COCH2CH3 + CH3COCH3 + CdCl2
(3) CH3COCH3 + CH3COCH3 + CdCl2
(4) CH3COCH3+CH3COCH2CH3+Cd(CH3) Cl
37. 32 65 CHCNX CHCHMgBr Dryether −≡→ What is X?
(1) CH6523 COCHCH
(2) CH653 COCH
(3) CH65CHO
(4) 2 652 CHCHCHCHO
38. The major product of the reaction is (1)
(4)
39. Choose the correct statement regarding Fries rearrangement?
(1) Acyl group attached to the ortho position of the benzene ring.
(2) Acyl group attached to the para position of the benzene ring.
(3) Acyl group attached to both ortho and para position of the benzene ring.
(4) Acyl group attached to meta position of the benzene ring.
Physical Properties
Single Option Correct MCQs
40. Arrange the following compounds in increasing order of their boiling points ?
I) CH3CHO
II) CH3CH2OH
III) CH3OCH3
IV) CH3CH2CH3
(1) IV < III < I < II
(2) III < IV < I < II
(3) IV < I < III < II
(4) III < IV < II < I
41. Which of the following statement in incorrect?
(1) Lower aldehydes have sharp pungent odours
(2) Methanol, ethanol and propanone are immiscible with water
(3) Many naturally occurring aldehydes and ketones are used in the blinding of perfumes
(4) Boiling points of aldehydes and ketones are lower than those of alcohols of similar molecular masses
42. Identify correct statements
A) Formaldehyde is a liquid
B) Acetaldehyde is soluble in water
C) Boiling point of ketones is greater than corresponding aldehydes
D) Lower aldehydes are pungent smelling
(1) A, B and D only
(2) B and D only
(3) A and C only
(4) B, C and D only
Chemical Reactions
Single Option Correct MCQs
43. Statement I : Aldehyde are more reactive than ketone.
Statement II : Nucleophilic addition reaction in carbonyl compound 1
Sterichindrance a and α positive charge at carbon of carbonyl group
(1) Statement I is true but Statement II is false
(2) Statement I is false but Statement II is true.
(3) Both Statement I and Statement II are true.
(4) Both Statement I and Statement II are false
44. The correct order of nucleophilic addition reaction among the following is
I) Benzaldehyde
II) p-Tolualdehyde
III) P-Nitrobenzaldehyde
IV) Acetophenone
(1) I > IV > III > II
(2) III > I > II > IV
(3) IV > II > I > III
(4) II > IV > I > III
45. Which of the following compounds is most reactive towards nucleophilic addition reactions?
(1)
(2)
(3) (4)
46. Statement I : Aldehydes and ketones react with water to form 1,1-diols, gem diols or hydrates
Statement II : Product formed are highly stable and can be easily isolated.
(1) Both statement I and statement II are correct
(2) Statement I is incorrect and statement II is correct
(3) Both statement I and statement II are incorrect
(4) Statement I is correct and statement II is incorrect
47. Statement I : Aldehydes and Ketones react with HCN to yield cyanohydrins.
Statement II : RCHO and RCOR reaction occurs very fast with pure HCN.
(1) If both statement I and statement II are true
(2) If statement I is true, statement II is false
(3) If statement I is false, statement II is true
(4) If both statement I and statement II are false
48. Acetaldehyde reacts with sodium bisulphide to form
(1) Acetyl chloride
(2) Ethyl chloride
(3) Ethylene chloride
(4) Acetaldehyde sodium bisulphite
49. Which of the following is least reactive towards Grignard reagent?
(1) HCHO
(2) CH3CHO
(3) CH3CH2CHO
(4) CH3-CO-CH3
50. Acetone is treated with excess of ethanol in the presence of HCl gas. The product obtained is:
(1) (2)
(3) (4)
51. What is the hybridization state of Carbon in functional group of ketals?
(1) sp3
(2) sp2
(3) sp
(4) One carbon is sp and another is sp 2
52. Acetaldehyde and acetone can be identified by
(1) Schiff’s reagent (2) Tollen’s reagent
(3) 2,4 – DNP test (4) Lucas test.
53. Which of the following gives oximes with acetaldehyde ?
(1) 22NHNH (2) 2, 4 – DNP
(3) 22 H NNHCONH (4) 2 NHOH
54. The compound formed by the reaction of propan-2-one (acetone) with hydrazine contains a (X) number of nitrogen atoms. Find the value of X?
(1) 2 (2) 4 (3) 1 (4) 3
55. The chemical reaction of acetone and phenylhydrazine results in:
(1) Ethylamine
(2) Hexamethylene tetra amine
(3) Acetone phenylhydrazine
(4) Acetone phenylhydrazone
56. When formaldehyde is treated with ammonia the compound formed is
(1) Urea
(2) Hexamethylene tetramine
(3) Bakelite
(4) Triethylene tetramine
57. Choose the correct statement reagrding Schiff’s base.
(1) It forms pink color with aldehyde and ketone.
(2) Both aldehyde and ketone respond positively with Schiff’s base test.
(3) Produced when carbonyl compounds react with amine.
(4) All the above
58. Match the reagents in column I with products formed by reactions with acetone in column II and mark the appropriate choice.
Column I Column II
A. Hydrazine I) (CH3)2C=NNHCONH2
B. Semicarbazide II) (CH3)2C=NOH
C. Phenyl hydrazine III) (CH3)2C=NNH2
D. Hydroxylamine IV) (CH3)2C=NNH(C6H5)
(A) (B) (C) (D)
(1) I II III IV
(2) IV III II I
(3) III I IV II
(4) II IV I III
59. Hexanal, 2-Hexanone, 3-Hexanone, Glucose. How many can give n-Hexane, when reduced with HI+RedP/ D ?
(1) 2 (2) 1
(3) 4 (4) 3
60.
Product formed in the above reaction is (1) (2)
(3) (4)
61. The Clemmensen’s reduction of benzaldehyde gives:
(1) 652CHNH (2) 65 CHOH
(3) 653CHCH (4) 65 CHCOOH
62. Identify ‘A’ in the following reaction.
(1) C N NH2 H2C C2H5 (2) C N NH2 H2C H2C (3) H2C CH3
(4) H2C
63. The appropriate reagent for the transformation is (1) Zn–Hg/HCl
(2) Red-phosphorus + HI
(3) LiAIH 4 (4) 1 and 2
64. CH3CHO is oxidised to CH3COOH using (1) Alkaline KMnO4 (2) Selenium oxide (3) Acidic KMnO4 (4) All
65. Acetone does not form
(1) A phenylhydrazone with phenylhydrazine
(2) A sodium bisulphite adduct with sodium bisulphite
(3) A silver mirror with Tollen’s reagent
(4) An oxime with hydroxylamine
66. The composition of Fehling solution A and Fehling solution B, respectively, is (1) Aqueous copper sulphate and alkaline sodium potassium tartarate (Rochelle salt)
(2) Alkaline sodium potassium tartarate (Rochelle salt) and alkaline copper sulphate
(3) Aqueous copper sulphate and acidic sodium potassium tartarate (Rochelle salt)
(4) Acidic sodium potassium tartarate (Rochelle salt) and aqueous copper sulphate
67. Aldehydes can be oxidised by (1) Benedict’s solution (2) Tollens’ reagent
(3) Fehling’s solution
(4) All of these
68. 4 3 AB NaOBr LiAlH CHCHO−→+→ C, ‘c’ is:
(1) CH3-OH (2) CH3CHO
(3) HCHO (4) H–COOH
69. Determine the products of the given reaction 3 3223 3O ConcHNOheat CHCHCOCHCH−−−−+→
(1) CH3CH2COOH + CH3COOH
(2) CH3COOH + CH3COOH
(3) CH3CH2CHO + CH3CH2OH
(4) CH3CH2COOH + CH3CH2OH
70. Acetone and acetaldehyde can be distinguished using (1) Grignard reagent (2) NaHSO3 (3) Ammonical AgNO3 (4) PCl5
71. The reagent which does not react with both, acetone and benzaldehyde
(1) Sodium hydrogensulphite
(2) Phenyl hydrazine
(3) Fehling’s solution (4) Grignard reagent
72. Haloform reaction is not given by (1) 33 CHCOCH (2) 325 H CHCOC
(3) 6525 CHH COC (4) 33 CHCHOHCH
73. Acetone on reaction with chlorine normally gives
(1) Mono chloro acetone
(2) Dichloro acetone
(3) Tri chloro acetone
(4) Hexa chloro acetone
74. The difference between aldol condensation and Cannizzro’s reaction is that :
(1) the former takes place in the presence of α-H-atom
(2) the former takes place in the absence of α-H-atom
(3) the former takes place in the presence of β-H-atom
(4) the former takes place in the absence of α-H-atom and β-H-atom
75. Reaction between acetaldehyde and acetophenone in presence of dilute NaOH followed by heating is known as
(1) Cross Aldol condensation
(2) Haloform reaction
(3) Cannizzaro’s reaction
(4) Cross Cannizzaro’s reaction
76. The reaction C6H5CHO + CH3CHO →
C6H5 CH = CH-CHO is called
(1) Benzoin condensation
(2) Claisen Schmidt reaction
(3) Perkin reaction
(4) Tishchenko reaction
77. Product of Perkin reaction is:
(1) α, β - unsaturated aldehyde
(2) β-cyclohexyl, α, β - unsaturated aldehyde
(3) β - Aryl -α, β - unsaturated acid
(4) α, g - unsaturated aldehyde
78. Cannizaro’s reaction is not given by
(1)
(2)
(3) HCHO
(4) CH3CHO
79. Acetaldehyde reacts with phosphorus pentachloride to form
(1) Acetyl chloride
(2) Ethyl chloride
(3) Ethylene chloride
(4) Ethylidene chloride
80. Aldehydes and Ketones can be distinguished by
(1) Neutral FeCl3 test
(2) Esterification reaction
(3) Litmus test
(4) Schiffs reagent test
Benzaldehyde
Single Option Correct MCQs
81. Give n below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Benzaldehyde on treatment with conc. HNO 3 and conc. H 2 SO 4 at 273K –283 K gives paranitro benzaldehyde.
Reason (R) : In benzaldehyde, –CHO group act as ring deactivating, meta directing group.
In light of the above statements, choose the correct answer from the options given below.
(1) A is false but R is true
(2) A is true but R is false
(3) Both A and R are true but R is not the correct explanation of A
(4) Both A and Rare true and R is the correct explanation of A
Nomenclature and Carboxylic Group
Single Option Correct MCQs
82. To preserve biological specimens the following is used
(1) 40% phenol
(2) 40% formaldehyde
(3) 40% Acetaldehyde
(4) 4% formaldehyde
83. Propionic acid can also be named as (1) Methyl methanoic acid
(2) Methyl acetic acid
(3) Methyl ethanoic acid
(4) Ethyl acetic acid
84. IUPAC name of valeric acid
(1) Propionic acid
(2) Burtyic acid
(3) Pentanoic acid
(4) 2-Methyl butanoic acid
85. Common name of Propane-1,3-dioic acid is _______.
(1) Malonic acid (2) Adipic acid
(3) Oxalic acid (4) Succinic acid
86. The IUPAC name of oxalic acid is (1) Ethane-1,2-dioic acid
(2) Propane-1,2-dioic acid
(3) Benzene-1, 2-diol
(4) Benzene-1, 3- dicarboxylic acid
87. Common name of 2-Aminobenzoic acid is _______.
(1) Anthranilic acid
(2) Methyl ethanoate
(3) Benzoic acid
(4) Amino benzoic acid
88. IUPAC name of salicylic acid is (1) 2-Hydroxybenzoic acid
(2) 3-Hydroxybenzoic acid
(3) 4-Hydroxybenzoic acid
(4) Benzoic acid
89. Match List - I with List - II
List – I List – II
A) Malonic acid P) HOOC–(CH2)2–COOH
B) Glutaric acid Q)
C) Pthalic acid R) HOOC–CH2–COOH
D) Succinic acid S)
T) HOOC–(CH2)3–COOH
(A) (B) (C) (D)
(1) P Q R S
(2) R T Q P
(3) R S T P
(4) R T S P
90. The IUPAC name of phthalic acid is (1) Benzene-1, 2-dicarboxylic acid
(2) Benzene-1, 4-dioic acid
(3) Benzene-1, 2-diol
(4) Benzene-1, 3- dicarboxylic acid
91. Common name of 1,2,3-benzene tricarboxylic acid is _______.
(1) Hemimellitic acid
(2) Trimesic acid
(3) Trimellitic acid
(4) Anthranilic acid
92. IUPAC name of Trimesic acid is ________.
(1) Benzene-1,3,5-tricarboxylic acid
(2) Benzene-1,2-dicarboxylic acid
(3) Benzene-1,3,4-tricarboxylic acid
(4) Benzene-1,3-dicarboxylic acid
93. Which of the following is a pair of functional isomers ?
(1) CH3COCH3, CH3CHO
(2) C2H5CO2H, CH3CO2CH3
(3) C2H5CO2H, CH3CO2C2H5
(4) CH3CO2H, CH3CHO
Preparation of Carboxylic Acids
Single Option Correct MCQs
94. Oxidation of primary alcohols finally gives (1) Aldehydes
(2) Ketones
(3) Carboxylic acids
(4) Esters
95. Identify compounds X and Y in the following sequence of reactions.
CH3CHO + HNO3 → X (1) C2H5OH (2) (CH3CO)2O
(3) CH3CO2H
(4) CH3CH2OH
96. Oxidation of But-2-ene with K2Cr2O7/H2SO4 along with heat finally gives
(1) One mole of ethanoic acid
(2) Ethanoic acid and formic acid
(3) 2 moles of ethanoic acid
(4) 2 moles of formic acid
97. Ethyl Benzene 4 2 (i)KMnO/OH (ii)H/HO ± → Predict X in above reaction
(1) C6 H 5 CH2 COOH
(2) C6 H 5 CH2 CHO
(3) Benzoic acid
(4) Benzaldehyde
Properties of carboxylic acids
Single Option Correct MCQs
98. Acetonitrile when boiled with alkali (or) acid gives
(1) CH3 COOH only
(2) CH3 COOH + C2 H 5 OH
(3) CH3 COOH + NH3
(4) CH3 COOH + H2
99. Hydrolysis of acetamide produces (1) Acetic acid (2) Acetaldehyde (3) Methyl amine (4) Formic acid
100. Which one of the following when reacts with CH3 MgBr followed by hydrolysis gives acetic acid?
(1) CO (2) CH3 CHO
(3) C2 H 5 OH (4) CO2
101. A 33 CHCOClCHCOOH →
What is A (1) H2 / Pd – BaSO4 (2) H2O
(3) SOCl2 (4) OsO4
102. 2 HO 65 A2CHCOOH: →
What is A (1) C6H5COOCOCH3 (2) (C6H5CO)2O
(3) C6H5CHO
(4) C6H5COC6H5
103. Which dicarboxylic acid in presence of a dehydrating agent is least reactive to give anhydride?
(1) (2) (3) (4)
104. Organic esters on hydrolysis yield
(1) alcohols
(2) carboxylic acids
(3) ethers
(4) both A and B
105. 3 ,HO 2 PhCONHB D+ →
Product (B) is
(1) Ph NH COOMe
(2) Ph NH COO Ph
(3) Ph NH COO Ph
(4) C6H5–NO2
106. (CH3)2 C = CH – COCH3 can be oxidised to (CH3)2 C = CH – COOH by (1) chromic acid
(2) KMnO4
(3) Cu at 575 K
(4) (i) NaOI and (ii) H+
107. 1-butyne on oxidation with hot alkaline KMnO4 would yield. Which of the following as end product?
(1) CH3CH2CH2COOH
(2) CH3CH2COOH
(3) CH3CH2COOH + CO2 + H2O
(4) CH3CH2COOH + HCOOH
108. Lower members of aliphatic carboxylic acid are soluble in water. This is due to (1) Formation of hydrogen bonds with water (2) Due to London forces (3) Water is non electrolyte (4) Van der-Waals interaction with water molecules
109. Which of the following possesses higher boiling point?
(1) C2H5Cl (2) CH3CHO
(3) C2H5OH (4) CH3COOH
110. Identify the correct order of melting points of the following compounds
(a) HCOOH (b) CH3COOH
(c) C6H5COOH
(1) a > b > c
(2) c > a > b
(3) a > c > b
(4) c > b > a
111. Which of the following exists as dimer in benzene?
(1) CH3 CHO (2) CH3 COCH3
(3) CH3 CH2 OH (4) CH3 COOH
112. Which among the following has a smell of rancid butter?
(1) CH3CH2CH2COOH
(2) CH3CH2COOH
(3) CH3COCH3
(4) CH3COOH
113. Which of the following is the strongest acid?
(1) CF3COOH
(2) CBr3COOH
(3) CH3COOH
(4) CCl3COOH
114. The correct acidic strength order of the following compounds is a) CH3COOH b) H2CO3
c) C2H5OH d) C6H5OH
e) H2O f) C2H2
(1) a > b > d > e > c > f
(2) a > d > c > b > e > f
(3) a > b > c > d > e > f
(4) a > b > d > c > e > f
115. The order of acidity of following acids is :
(1) ii > iii > iv > i (2) iii > ii > i > iv
(3) iv > ii > iii > i (4) iv > iii > ii > i
116. Acetic acid is treated with metallic Sodium to form Hydrogen and X. When X is treated with Sodalime, Y and Sodium Carbonate are formed. ‘Y’ is (1) C2H6 (2) CH4 (3) CH3COONa (4) CH3CONH2
117. In which of the following reaction CO 2 gas will evolve?
(1) (2)
(4)
118. () NaOHandCaOSodalime RCOONaHeat23 ANaCO−→+
In the above reaction A is (1) R–OH (2) R–COOH (3) R–H (4) RCHO
119. Acetic acid gives acetic anhydride when treated with (1) PCl5 (2) P2O5 (3) Cl2/P (4) Na
120. A fruity smell is produced by the reaction of C2H5OH with (1) PCl5 (2) CH3COCH3 (3) CH3COOH (4) NaOH
121. In esterification, concentrated H 2SO4 acts as
(1) Catalyst
(2) Dehydrating agent
(3) Hydrolysing agent
(4) Both as a catalyst and dehydrating agent
122. Acetyl chloride is not obtained from acetic acid by the action of (1) SOCl2 (2) CHCl3 (3) PCl3 (4) PCl5
123. X 33 CHCOOHCHCOCl →
Here the reagent X can not be (1) PCl5 (2) PCl3
(3) SOCl2
(4) NaCl
124. X 333 CHCOOHCHCOClPOClHCl →++
Here the reagent X can not be (1) PCl5 (2) PCl3 (3) SOCl2 (4) NaCl
125. In the following reaction, X and Y are respectively
332 CHCOOHNHXYHO +D→→+
(1) CH3CONH2; CH4
(2) CH3COONH4; CH3CONH2 (3) CH3CONH2; CH3COOH (4) CH3NH2; CH3CONH2
126. CH 3CO 2C 2H 5 on reaction with conc. NH3 forms
(1) Carboxylic acid
(2) Acetamide
(3) Aldehyde
(4) Anhydride
127. The reagent used for converting ethanoic acid to ethanol is (1) LiAlH 4 (2) H2 /Ni
(3) PCl3 (4) NaBH4
128. Acetic acid liberates CO 2 gas with (1) Na (2) Zn (3) NaHCO3 (4) NaOH
129. CH3–COO–K+ electrolysis → product. Which of the following hydrocarbon formed in this reaction
(1) ethane (2) CH3COOCH3 (3) CH3CH2CH2CH3 (4) CH3CH2–CH3
130. 2 Br/reflux 6565 CHCOOAgCHBrXAgBr →++
What is X in the above reaction?
(1) CO2 (2) CO (3) AgO (4) CH3Br
131. What is the reagent used in the preparation of chloro-acetic acid from acetic acid?
(1) PCl5 (2) Cl2 / Red P (3) PCl3 (4) SOCl2
132. Which of the following reaction represents the Hell – Volhard – Zelinsky reaction?
(1)
(2) (3) (4)
133. Select the correct statement.
(1) During bromination of benzene, the major poroduct is 3-bromobenzoic acid
(2) -COOH group is an electron-withdrawing group, hence it is para-directing group
(3) During sulphonation of benzene, the major poroduct is 2-Sulphobenzoic acid.
(4) Catalyst using in bromination of benzoic acid is conc. HNO3.
134. Benzoic acid do not undergo Friedel – Craft’s reaction because
(1) Carboxyl group is a strong electronwithdrawing group.
(2) Lewis acid itself is attached to the benzene ring.
(3) Both 1 and 2
(4) Neither 1 nor 2
135. The major product of sulphonation of benzoic acid is
(1) 3-Sulphobenzoic acid
(2) 4-Sulphobenzoic acid
(3) 2-Sulphobenzoic acid
(4) 2,4-Disulphobenzoic acid
136. The major product of nitration of benzoic acid is
(1) 3 - Nitro benzoic acid
(2) 4 - Nitro benzoic acid
(3) 2 - Nitro benzoic acid
(4) 2, 4 - Dinitro benzoic acid
137. The carboxylic acid that reduces Tollen’s reagent is
(1) Acetic acid (2) Benzoic acid
(3) formic acid (4) Malic acid
138. Acetic acid can be used
A) For curing meat and fish
B) As vinegar in cooking
C) In the preparation of perfumes
(1) Only A (2) Only B
(3) Only C (4) All
139. The compound which is widely used as acetylating agent is
(1) glacial acetic acid
(2) ethyl acetate
(3) acetic anhydride
(4) anhydrous sodium acetate
Level - II
Namenclature and Structure of Carbonyl Group
Single Option Correct MCQs
1. The hybridisation of carbon in the carbonyl group is (1) sp3 (2) sp2 (3) sp (4) sp3d
2. The IUPAC name of β-methylvalerladehyde
(1) 2- methyl pentanal (2) 2-methyl butanal (3) 3-methyl pentanal (4) 3- methyl butanal
3. The IUPAC name of the following compound is
(1) 5-bromo-3 hydroxy benzene carbaldehyde
(2) 3-bromo-5 formyl phenol
(3) 3-bromo-5-hydroxy benzene carbaldehyde
(4) 1-bromo-3 formyl-5-hydroxyl benzene
4. 2–Pentanone and 3–methylbutan-2-one are
(1) optical isomers (2) geometrical isomers (3) chain isomers (4) tautomers
5. The number of structurally isomeric ketones with formula C6H12O is (1) six (2) two (3) five (4) four
6. The IUPAC name of α-methyl valeraldehyde is (1) 2-methyl pentanal (2) 3-methyl pentanal
(3) 2-methyl butanal (4) 3-methyl butanal
7. Formula of benzoin is (1) C6H5−CO−C6H5 (2) C6H5−CO–CHOH−C6H5 (3) C6H5−CH2−CHO (4) C6H5−CO−CH3
Numerical Value Questions
8. The number of structurally isomeric ketones with formula C6H12O is ____.
9. The number of carbonyl carbon atoms present in cyclohexane-1,3,5-trione is ___.
Preparation of Aldehydes and Ketones
Single Option Correct MCQs
10. 2 3 24 Hg CHCCH x dilHSO + −≡→ (Carbonyl compound). The number of sigma, pi bonds and lone pairs of electrons in x are, respectively (1) 9, 2, 2 (2) 6, 1, 2 (3) 9, 1, 2 (4) 9, 2, 3
11. The reagent used in Stephen’s reaction is (1) Zn + HCl (2) LiAlH4/H2O (3) Pd−BaSO4/quinoline (4) SnCl2+HCl
12.
Reactant
Reagent Product
(I) Propene (P) aq.KOH (A) CH3–CO–CH3 (II) Propyne (Q) H2/Pd− BaSO4 (B) CH3–CHO
(III) 1,1-dichloro propane (R) H3O+/Hg2+ (C) HCHO
(IV) Propanoyl chloride (S) O3/ Zn+H2O (D) CH3–CH2–CHO
(1) I- R,D (2) II- S,A (3) III- P,B (4) IV-Q,D
13. In which of the following process acetone is one of the final products?
(1) Ozonolysis of ethyne
(2) Oxidation of 2-butene with KMnO 4/H+
(3) Oxidation of 2,3–dimethyl–2–butene with KMnO4/H+/∆
(4) Dehydrogenation of 1-propanol
14. Calcium acetate on heating results in (1) Acetone (2) Acetaldehyde (3) Ethane (4) Acetic anhydride
15. The most suitable reagent for the conversion of RCH2OH → RCHO is (1) K2Cr2O7 (2) CrO3 (3) KMnO4 (4) PCC
16. 3 Anhyd. AlCl 66 CH+CO+HCl X+HCl →
Compound 'X' is (1) C6H5CH3 (2) C6H5CH2Cl (3) C6H5CHO (4) C6H5COOH
Numerical Value Questions
17. A diene on reductive ozonolysis produces two moles of ethanal and one mole of propan -1, 3-dial. How many geometrical isomer(s) is/are possible for the diene?
18. 322 (5.6g) HCCHCHCH −−=
1) Hg(OAC),HO
then the mass of 'B' formed in the reaction is _____
19. The number of chiral centres present in [B] is _____
Number of sp2–C atoms present in 'X' ___.
Physical Properties
Single Option Correct MCQs
21. Identify correct statements
(A) Formaldehyde is a liquid.
(B) Acetaldehyde is soluble in water.
(C) Boiling point of ketones is greater than corresponding aldehydes.
(D) Lower aldehydes are pungent smelling.
(1) A, B, and D only (2) B, and D only
(3) A, and C only (4) B, C, and D only
Chemical Reactions
Single Option Correct MCQs
22. The increasing order of the reactivity of the following compounds in nucleophilic addition reaction is: propanal, benzaldehyde, propanone, butanone
(1) benzaldehyde < butanone < propanone < propanal
(2) butanone < propanone < benzaldehyde < propanal
(3) propanal < propanone < butanone < benzaldehyde
(4) benzaldehyde < propanal < propanone < butanone
23. Consider the following reaction: propanal+methanal () 583 3 (i) dil. NaOH (ii) Product B (iii) NaCN CHO (iv)HO B + D
The correct statement for product B is.
(1) It is a racemic mixture and gives a gas with saturated NaHCO3 solution.
(2) It is a racemic mixture and neutral.
(3) It is a optically active alcohol and is neutral.
(4) It is a optically active and adds one mole of bromine.
24. How many molecules of RMgX are consumed in the below reaction?
(1) 2 (2) 4 (3) 5 (4) 6
25. Which of the following reaction will not involve in the formation of carbon – carbon bond
(1) Reimer–Tiemann reaction
(2) Friedel–Craft reaction
(3) Wurtz reaction
(4) Cannizzaro reaction
26. The major product obtained in the following reaction is:
27. Product of the following reaction is:
28. Find the product of the given reaction:
29. O + II H 222 R-CH=CH-CHO+NH-C-NHNHX → (X) in the above reaction is
(1) OH I 22 H-CH-CH-CH-NHCONHNH
(2) || 2 O R-CH=CH-CH=N-NH–C–NH
(3) R−CH=NH2CONH2
(4) I 22 OH R-CH=CH-CH-NHCOCH=NHNH
30. Which among the following is most reactive to give nucleophilic addition?
(1) FCH2−CHO (2) ClCH2−CHO (3) BrCH2−CHO (4) ICH2−CHO
31. Iodoform test is not answered by ___. (1) CH3CHO
(2) 3–pentanone
(3) CH3COCH3 (4) CH3CHOHCH2C6H5
32. Arrange in their increasing order of equilibrium constants for hydration.
(A) CH3COCH3 (B) CH3CHO
(C) CH3COCH2CH3 (D) HCHO
(E) ClCH2CHO
(1) A < B < C < D < E
(2) A < C < B < E < D (3) A < C < E < B < D (4) C < A < B < E < D
33. Which one of the following gives orange (or) red colour with 2, 4-DNP, yellow ppt with Na2CO3+I2 and red ppt with Fehling’s reagent ?
(1) CH3CHO (2) C6H5CHO (3) CH3COCH3 (4) C6H5CH2CHO
34. Fehling’s solution is (1) acidified copper sulphate solution (2) ammonical cuprous chloride solution (3) copper sulphate and sodium hydroxide + Rochelle salt
(4) ammonical AgNO3 solution
35. Major products of the following reaction are:
and HCOOH (4) CH3OH and HCO2H
36. Formaldehyde can be distinguished from acetaldehyde by the use of:
(1) Schiff reagent (2) Tollens' reagent
(3) I2/Alkali
(4) Fehling’s solution
Numerical Value Questions
37. How many of the following reduce Fehling's solution? Formic acid, formaldehyde, benzaldehyde, sucrose, fructose, glucose, acetone
38. Aromatic carbonyl compounds having molecular formula C 8 H 8 O react with NH 2OH. How many isomeric oximes can be formed?
39. Among the following how many gives NaHSO3 addition reaction?
(i) O II 3 C-H CH(ii) O CH
(iii)
(vii)
40. Number of isomeric structural compounds with molecular formula C 9 H 10 O, which (i) do not dissolve in NaOH (ii) do not dissolve in HCl (iii) do not give orange precipitate with 2, 4-DNP (iv) on hydrogenation give identical compound with molecular formula C9H12O is __________.
Benzaldehyde
Single Option Correct MCQs
41. Among the following the number of reaction (s) that produce(s) benzaldehyde is
CO, HCl
I)
Anhydroces AnhydrousAlCl3AlCl3 II)
O
C
Me
BaSO 4
- H
- 78o C
42. Oxidation of toluene to benzaldehyde can be easily carried out with which of the following reagents?
(1) CrO3/acetic acid, H3O+
(2) CrO3/acetic anhydride, H3O+
(3) KMnO4/HCl, H3O+
(4) CO/HCl, anhydride, AlCl3
43. The final product obtained when toluene is subjected to side chain chlorination followed by hydrolysis at 737 K is
(1) phenol (2) benzaldehyde
(3) acetophenone (4) chlorobenzene
44. Which of the following compounds will undergo cannizaro reaction?
(1) CH3CHO (2) CH3COCH3 (3) C6H5CHO (4) C6H5CH2CHO
45. Salicylaldehyde reacts with acetic anhydride in presence of sodium acetate to give a compound which on acidification followed by treatment with concentrated sulphuric acid gives coumarin which is used to make many anticoagulant drugs. The structure of coumarin is (1)
46. 1-Phenylethanol can be prepared by reaction of benzaldehyde with (1) methyl bromide
(2) ethyl iodide and magnesium
(3) methyl bromide and aluminium bromide
(4) methyl iodide, Mg and hydrolysis
Numerical Value Questions
47. () 3 65 3 2
Number of sp2 carbon atoms in product is
48. The sum of degree of unsaturation and the number of sp 2 carbon atoms of the final product U of the following reaction sequence is
(D) HOOC–CH 2 –CH(COOH)–CH 2 –COOH–Tricarballylic acid
(1) A, B, C and D
(2) A, B and D only
(3) B and D only
(4) A, C and D only
52. The IUPAC name of compound
CH2 C OH CH 2 COOH OH C COOH O is:
(1) 1,2,3-tricarboxypropane-2-ol
Nomenclature and Carboxylic Group
Single Option Correct MCQs
49. How many of the following compounds contains –COOH group?
(a) Sulphanilic acid
(b) Picric acid
(c) Aspirin
(d) Ascorbic acid
(1) 1 (2) 2 (3) 3 (4) 4
50. The IUPAC name for methyl acetate is (1) ethoxymethane (2) methyl ethanoate (3) ethylmethanoate (4) methyoxy ethane
51. Identify correct match from the following:
(A) (CH2 )3
(2) 2-hydroxy propane-1,2,3-tricarboxylic acid
(3) 3-hydroxy-3-carboxypent-1,5-dioic acid
(4) None of the above
53. IUPAC name of phthalic acid is (1) benzene-1, 4-dicarboxylic acid
(2) benzene-1, 2-dicarboxylic acid
(3) benzene-1, 3-dicarboxylic acid
(4) 2-Phenylethanoic acid
Numerical Value Questions
54. Citric acid contains X carboxylic groups and Y hydroxyl groups. Value of X + Y is
55. Give the total isomers of the carboxylic acid with molecular formula C 5 H10O2.
56. Number of benzene ring containing aldehydes are possible wih M.F. C 8 H8O
Preparation of Carboxylic Acids
Single Option Correct MCQs
57. CH3CH2CH2CONH2 is boiled with aqueous NaOH, then the reaction mixture is acidified with HCl. Products obtained are
(1) CH3CH2CH2COO– + NH3
(2) CH3CH2CH2COONa + NH3
(3) CH3CH2CH2COOH + NH4Cl
(4) CH3CH2CH2COO– + NH4Cl
58.
Ethylbenzene
Produced X in the reaction is
(1) PhCH2COOH (2) PhCH2CHO
(3) Benzoic acid (4) Benzaldehyde
59. Which of the following would be the best synthesis of 2,2-dimethyl propanoic acid?
In the above reaction 'Z' can not be (1) −CH3 (2) −C3H5 (3) −C(CH3)3 (4) −CH(CH3)2
61. The acid D obtained through the following sequence of reactions is:
(1) Succinic acid (2) Malonic acid (3) Maleic acid (4) Oxalic acid
62. Which one of the following reactions will not yield propionic acid?
(1) CH3CH2CCl3+OH /H3O+ (2) CH3CH2COCH3+IO /H3O+
(3) CH3CH2CH2OH+KMnO4/H+
(4) CH 3 CH 2 CH 2 Br+Mg+CO 2 dry Ether/ H3O+
63. Identify C in the following sequence of reactions:
3 34 POHO CHCOONHABC D+ →→→
(1) CH3CH2CONH2 (2) CH3CN
(3) (CH3CO)2O (4) CH3COOH
64. Chlorination of Toluene in the presence of light and heat followed by treatment with aqueous NaOH gives
(1) o-Cresol
(2) p-Cresol
(3) 2, 4-Dihydroxytoluene (4) Benzoic acid
Numerical Value Questions
65. How many mole of H-COOH is formed, due to the oxidation with HIO 4 of, R - CH - CH - CH - CH2 OH OH OH OH
66. The total number of carboxylic groups in the product is ___.
O O O O
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
67. How many different carboxylic aids are obtained when all isomeric arenes having the molecular formula C8H 10 are oxidised by alkaline KMnO4 followed by acidification.
Properties of carboxylic acids
Single Option Correct MCQs
69. Which of the following compound loses CO2 upon heating to 100°C (1)
70.
In a given reaction, what is ‘X’ for fastest reaction
(1) −NO2 (2) –Cl (3) –CH3 (4) –CHO
71. A fruity smell is produced by the reaction of C2H5OH with (1) PCl5 (2) CH3COCH3 (3) CH3COOH (4) NaOH 72. 2 excess Cl 32 Re . H dP CHCNHOAB + D +→→ in this reaction, A and B are, respectively (1) CH3COOH, CCl3COOH (2) CH3CH2OH, CH3CH2Cl (3) CH3CHO, CCl3CHO (4) CH3COCH3, CCl3COCH3
73. The major product of the following reaction
(3)
(4)
(2)
74. Which of the following is most reactive towards nucleophilic acyl substitution?
(1) CH3COCl (2) (CH3CO)2O
(3) CH3COOCH3 (4) CH3CONH2
75. The decreasing order of ease of alkaline hydrolysis for the following ester is
(3) CH3COOH and CH3COCH3
(4) CH3COCH3 and HCOOH
77. The correct order of acid character of the following compounds is OH COOH COOH COOH
(1) III > II > IV > I (2) III > II > I > IV
(3) IV > II > III > I (4) II > III > I > IV
76. Compounds X and Y give effervescence with NaHCO 3 solution, X gives a silver mirror with ammonical AgNO 3 , while Y gives a sweet smelling compound on heating with alcohol in the presence of H 2SO4. X and Y are
(1) HCOOH and CH3COOH
(2) CH3CHO and CH3COOH
(i) (ii) (iii) (iv)
(1) III > II > I > IV
(2) IV > III > II > I
(3) I > II > III > IV
(4) II > III > IV > I
78. The correct order of their reactivity towards hydrolysis at room temperature is:
(A) O R Cl (B) O R O R O (C) O R O R
(D) O R N H H
(1) (D) > (B) > (A) > (C)
(2) (D) > (A) > (B) > (C)
(3) (A) > (C) > (B) > (D)
(4) (A) > (B) > (C) > (D)
79. H H OAC COOEt
Major product of the reaction is
COOEt (2) COOEt (3) OAC (4) OAC
Numerical Value Questions
80. The number of compounds which are more acidic than ethanoic acid among the given are CCl 3 COOH, C 6 H 5 COOH, HCOOH, (COOH) 2, CH 3COOH, CH 3COCOOH, 2, 4, 6-trinitro phenol
81. The number of correct statements among the following is
i) Methanoic acid is used in rubber, textile, dyeing, leather and electroplating industries
ii) Ethanoic acid is used as solvent and as vinegar in food industry
iii) Hexanedioic acid is used in the manufacture of nylon-6,6
iv) Esters of benzoic acid are used in perfumery
v) Sodium benzoate is used as a food preservative.
vi) Higher fatty acids are used for the manufacture of soaps and detergents
82. Amongst the following the total number of compounds soluble in aqueous NaOH is
83. When Z-isomer of cinnamic acid is reacted with SOCl2 followed by hot anhydrous AlCl3 and finally with Zn-Hg in concentrated HCl, the molar mass of the organic hydrocarbon finally obtained is _______ g.
84. How many of the following carboxylic acids show H.V.Z reaction. CH 3 COOH, CH 3 CH2COOH, (CH3)3C-COOH
Single Option Correct MCQs
85. Which of the following can show both tautomerism and optical isomerism
86. The major product of the following reaction is:
87. The major product obtained in the reaction of bromobenzene with Mg in dry ether followed by reaction with benzonitrile and hydrolysis is.
(1) Acetophenone
(2) Benzophenone
(3) Phenyl benzoate
(4) Benzoic acid
88. The major product (P) in the following reaction is:
89. Consider the reactions
Identify A, X, Y & Z.
(1) A=methoxy methane, X=ethanol, Y=ethanoic Acid, Z=semicarbazide
(2) A=ethanal, X=ethanol, Y=But-2-enal Z=semicarbazide
(3) A=ethanol, X=acetaldehyde, Y=butanone Z=hydrazone
(4) A=methoxymethane, X=ethanoic acid, Y=acetate ion, Z=hydrozine 90. C RO O
Find the reactivity order with LiAlH 4
(1) A > B > C > D (2) B > C > D > A (3) D > C > B > A (4) B > D > C > A
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
91. The compound shown below undergoes racemisation on reaction with aqueous acid.
OH
Which of the following structure best represents the intermediate responsible for this process?
92. Which of the following compound would be most reactive for Perkin condensation with acetic anhydride?
94. Which of the following ketone will not give enamine on treatment with secondary amines? [where t-Bu is−C(CH3)3]
93. The product X, and Y are, respectively.
95. Consider the above reaction sequence and identify the product B
96. Isobutyraldehyde on reaction with formaldehyde and K2CO3 gives compound 'A'. Compound ‘A’ reacts with KCN and yields compound ‘B’, which on hydrolysis gives a stable compound ‘C’. The compound 'C' is (1)
(2)
(4)
Which among the above compound/s does/ do not form silver mirror when treated with Tollens' reagent?
(1) (I), (III) and (IV) only
(2) Only (IV)
(3) Only (II)
(4) (III) and (IV) only
98. 22 i) Cl, ii) CN iii)HO/H A + D → p-Bromophenyl acetic acid. in the above reaction ‘A’ is
99. The most appropriate reagent(s) for the following conversion is N O CO2 Me N
?
(1) LiAlH 4 (2) NaBH4
(3) Zn(Hg)HCl
(4) BH3/THF
Numerical Value Questions
100. Birch reduction of toluene leads to a product with molecular formula C 7 H 10 . On ozonolysis followed by reduction with dimethyl sulphide, two products X and Y are obtained. Number of active methylene hydrogens present in X = a and in Y = b. Then find a + b.
101. Br CH3 CH 3 C H3 + 3 32 1.Mg/Dryether 2.HCHO/HO 3.PCC 4.O/Zn/HO → Product
In the product number of tetrahedral stereo centers are (X) , number of sp2 carbon atoms are (Y) and degree of unsaturation is (Z). Find the value of (X)+(Y)–(Z) is _____.
102. A hydrocarbon ‘X’ is found to have molar mass of 80. A 10.0 mg of compound ‘X’ on hydrogenation consumed 8.40 mL of H2 gas (measured at STP). Ozonolysis compound ‘X’ yields only formaldehyde and dialdehyde. The total number of fragments/molecules produced from the ozonolysis of compound ‘X’ is ___.
103. Consider the following sequence of reaction.
1. CH3CH2CH2Cl; AlCl3
2. O2, light
3. H+ / Δ
2 [yellowppt] NaOH l BCD →+
Conc.CHSO24
E
(2 mol) (2
All molar mass are expressed in g mol−1[molar mass of C = 12, H =1, O= 16]
molar mass of E is x (g mol−1)
molar mass of F is y (g mol−1) molar mass of H is z (g mol−1).
Find (x + y + z).
104. How many of the following reactions involve in C–C bond formation?
i) Reimer–Tiemann reaction
ii) Friedel–Crafts reaction
iii) Wurtz reaction
iv) Cannizzaro reaction
105. 3 23 dil acid CHCHCHOCHCHXY =→ −−+
(Y gives positive haloform test) The number of possible isomers for X excluding stereo isomers and including X.
106. The number of compounds giving (i) red colouration with ceric ammonium nitrate and also (ii) positive iodoform test from the following is _____.
107. What is the total number of lone pairs in the final product (X) of the given reaction.
108. In the following reaction sequence, the amounts of D and G (in g) formed from 10 mole of acetophenone are x and y. Then calculate (x + y) (Atomic weight in g mol–1; H = 1, C = 12, N = 14, O = 16, Br = 80. The yield (%) corresponding to the product in each step is given in the parenthesis)
109. 6 4.2 g of acetic acid is added to excess of sodium. The volume of gas liberated at STP
Level - III
1. An organic compound “A” with molecular formula C 8 H 8 O forms an orange red precipitate with 2,4-DNP reagent and gives yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens or Fehlings reagent, nor does it decolourises bromine water or Baeyer’s reagent. On drastic oxidation with chromic acid, . It gives a carboxylic acid (B) having molecular formula C 7H6O2. Degree
of unsaturation of compound (A) and (B) respectively are
(1) 5, 5 (2) 4, 4
(3) 3, 5 (4) 3, 3
2. The correct order of acidity for the following compounds is
(1) I > II > III > IV
(2) III > I > II > IV
(3) III > IV > II > I
(4) I > III > IV > II
3. The major product of the following reaction is
(1) (2) (3) (4)
4. Identify the reagents used for the following conversion
(1) A = LiAlH4, B = NaOH(aq), C = NH2−NH2/ KOH, Ethyleneglycol
(2) A = DIBAL–H, B = NaOH(alc), C = NH2
NH2/KOH, Ethyleneglycol
(3) A = DIBAL–H, B = NaOH(alc), C = Zn/ HCl
(4) A = LiAlH4, B = NaOH(alc), C = Zn/HCl
5. In the given reaction sequence, [M] is all possible (including stereoisomers) five and six member cyclic esters (Lactones).
Find the value of [M] (1) 10 (2) 4 (3) 9 (4) 8 6. . The structure of compound ‘F’ is: (1) (2) (3) (4)
7. Choose the answer that has the following compounds located correctly in the separation scheme.
(1) phenol is in (Z); phenylacetic acid is in (X); Toluene is in (Y)
(2) toluene is in (Y); phenylacetic acid is in (Y); phenol is in (Z)
(3) phenylacetic acid is in (X); toluene is in (Z); phenol is in (Y)
(4) toluene is in (Z); phenylacetic acid is in (Y); phenol is in (X)
8.
X and Y are respectively
(1) H2/Pd−BaSO4; PCC
(2) H2/Ni, Δ; [Ag(NH3)2]+/H+
(3) H2/Pt, 298K; NaOI/H+ (4) LiAlH4;CrO2Cl2+Cs2; H3O+
9. Which of the following is the correct formula of the compound A used with benzaldehyde; in order to synthesise the product given in the reaction?
10. Photo catalyzed mono bromination of toluene gives ‘A’. The compound ‘A’ on treatment with aqueous NaOH Gives ‘B’. The compound ‘B’ on treatment with SOCl2 Gives ‘C’. The compound ‘C’ is reacted with KCN followed by hydrolysis and heat gives ‘D’. The major product ‘D’ is.
11. The compound A in the following reactions is:
(1)
(2) (3) (4)
(4)
12. The major product of the following reaction sequence is
13. The major product formed in the following reaction sequence is
(1)
(2)
(3)
(4)
(1)
(2)
(3)
(4)
14. The principal organic product [P] in the following reaction sequence is
16. Identify the reagents (1-4), required for the transformation shown and arrange them in correct order.
(1) LAH (2) OsO4
(3) LTA or HIO4 (4) NaBH4
(1) 1 → 3 → 4 → 2
(2) 2 → 3 → 1 → 4
(3) 2 → 1 → 3 → 4
(4) 1 → 2 → 3 → 4
17. 12.0g of acetophenone on reaction with 76.2g of iodine in presence of aq. NaOH gave solid A in 75% yield. Approximate amount of A obtained (in gram) in the reaction is [atomic wt of I=127].......
18. Find the number of atoms that use only pure atomic orbitals in the bond formation in the product “W”
19. In the following reaction sequence, the amounts of D & G (in g) formed from 10 moles of acetophenone are ‘x’ & ‘y’. Then calculate (x + y) (Atomic weight in g mol-1; H = 1, C = 12, N = 14, O = 16, Br = 80. The yield (%) corresponding to the product in each step is given in the parenthesis)
20. Consider the following reactions
The mass percentage of carbon in A is
21. The total number of sigma and pi bonds in the chief organic product of the following reaction is
22. Assume that the reaction of MeMgBr with ethylacetate proceeds with 100% conversion to give tert-butanol. The volume of 0.2 M solution of MeMgBr required to convert 10mL of a 0.025 M solution of ethyl acetate to tert-butanol is _____ mL. (Round off to one decimal place)
25. If the number of sp2 hybridized carbon atoms in compound [R] of the following reaction sequence is N, the value of 10 2 N is____.
26. The number of oxygen atoms in product [P] is
23. . If B is
Maximum number of moles of AC 2 O Consumed by reactant (A) is
24. How many of the following compounds give racemic mixture with CH3MgCl.
27. How many of the following molecules will give acetone as one of the products of ozonolysis?
28. The number of pi electrons which do not contribute to aromaticity in the product of the following reaction is
THEORY BASED QUESTIONS
Statement Type Questions
Each question has two statements: statement I (S-I) and statement II (S-II). Mark the correct answer as
(1) if both statement I and statement II are correct.
(2) if both statement I and statement II are incorrect.
(3) if statement I is correct, but statement II is incorrect.
(4) if statement I is incorrect, but statement II is correct.
1. S-I : Tropolone is an aromatic compound and has 8π electrons.
S-II : π electrons of > C = O group in tropolone is involved in aromaticity.
2. S-I : Formaldehyde is more reactive than benzaldehyde for nucleophilic addition reaction.
S-II : Formaldehyde is more volatile than benzaldehyde.
3. S-I : Lower aldehydes and ketones are soluble in water.
S-II : Lower aldehydes and ketones form intermolecular H – bonding with water.
4. S-I : O OH can be easily reduced using Zn-Hg/HCl to CH3 CH3
S-II : Zn-Hg/HCl is used to reduce carbonyl group to – CH2 – group
Assertion and Reason Questions
In each of the following questions, a statement of Assertion (A) is given, followed by a corresponding statement of Reason (R). Mark the correct answer as
(1) if both (A) and (R) are true and (R) is the correct explanation of (A) .
(2) if both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) if (A) is true but (R) is false .
(4) if both (A) and (R) are false.
5. (A) : Formaldehyde is a planar molecule
(R) : Carbon atom in formaldehyde is sp 2 - hybridised.
6. (A) : Phenoxide ion is more stable than carboxylate ion hence phenol is more acidic than carboxylic acids.
(R) : The negative charge is delocalised over two electronegative oxygen atoms and one carbon in carboxylate ion.
7. (A) : Carboxylic acids are higher boiling liquids than aldehydes, ketones and even alcohols of comparable molecular masses.
(R) : More extensive association of carboxylic acid molecules occur through intermolecular hydrogen bonding.
8. (A) : The boiling points of aldehydes and ketones are higher than hydrocarbons and ethers of comparable molecular masses.
(R) : Aldehydes and ketones are with weak molecular association due to dipole–dipole interactions.
9. (A) : The melting point of monocarboxylic acid with even number of carbon atoms is higher than that of with odd number of carbon atoms acid immediately below and above it in the series.
(R) : The solubility of monocarboxylic acids in water decreases with increase in molar mass.
10. (A) : Acetal/ketal is stable in basic medium.
(R) : The high leaving tendency of alkoxide ion gives the stability to acetal/ketal in basic medium.
11. (A) : Compounds containing –CHO group are easily oxidised to corresponding carboxylic acids.
(R) : Carboxylic acids can be reduced to alcohols by treatment with LiAlH 4
JEE ADVANCED LEVEL
Multiple Option Correct MCQs
1. An ester A (C 4 H 8 O 2 ) on treatment with excess CH3MgBr followed by work-up gives an alcohol B as the only product. Which of the following statement is/are true?
(1) A on basic hydrolysis gives formate ion as one of the products.
(2) Alcohol B gives positive iodoform test.
(3) A on acidic hydrolysis gives acetic acid as one of the product.
(4) Alcohol B gives precipitate with Lucas reagent immediately.
2. Suitable reagent for the given conversion is/ are:
12. (A) : CH 3 −CH 2 −CN on hydrolysis gives ethanoic acid.
(R) : Cyanides on hydrolysis gives NH3 and carboxylic acid.
(3) ‘Y’ product liberate CO2 gas with aqueous NaHCO3 and also soluble in aqueous NaOH
(4) ‘Z’ product is resolvable
The major products formed in this reaction are
(1) LiAlH 4 (2) NaBH4
(3) B2H6/THF (4) H2/Pd-C
Identify correct statement for above reaction sequence?
(1) ‘Z’ product is sweet smelling substance
(2) Reaction of
hemiketal product
5 An ester A(C 4 H 8 O 2 ) on treatment with excess CH 3 MgBr followed by treatment with aqeous NH4Cl gives an alcohol ‘B’ as the only product. Which of the following statement is/are true?
(1) A on basic hydrolysis gives formate ion as one of the products.
(2) Alcohol B gives positive iodoform test.
(3) A on acidic hydrolysis gives acetic acid as one of the product.
(4) Alcohol B gives precipitate with Luca’s reagent immediately.
6. Vanillin (L) C8H8O3 is isolated from vanilla beans. It gives an intense colour with FeCl 3 and a positive Tollen's test. It is not steamdistilled and does not react with HCl. It goes through the following steps:
L Among the following pair(s) which can be distinguished by aq. NaHCO 3 is/are:
(1) M, N
(2) N, P
(3) L, O
(4) P, O
(1) CH3COOH (2) CH3 OH
(3) Me3C−OH (4) Me3−C−18OH
8. Compounds that can give aldol product with aq.NaOH is/are:
(1) O (2) CH3–CO–CCl3 (3) CH3CH2COCH3 (4) PhCH2CHO
9. In which of the following reaction(s) benzaldehyde is obtained as a product?
(1) i) CrO2 Cl2 , CS2 ii) H2 O CH3
i) (i-Bu)2 A1H - 780 C ii) H2 O C N 2 2 i) (iBu)AlH78C ii) H0 →
i) CrO3 (ii) H2 O CH3 (CH3 CO)2 O ,
i) LiBH (ii) H 2O OEt O
10. The major product(s) in the reactions
11. Which of the following is/are corre ct reaction?
(1) CH3MgBr+CH3−CH2−OH → CH4+
CH3−CH2−OMgBr
(2) CH3–CH2MgBr+
CH3COCH2CH3 O ether 323 II CH-C-CH-CH →
(4) Acetophenone on oxidation with alkaline KMnO 4 followed by hydrolysis gives Benzoic Acid.
12. Identify the reagents (1-4), required for the transformations shown and arrange them in the correct order.
13. Which of the following pairs can be differentiated by Tollen’s reagent?
P) LiAlH 4
Q) OsO4/NaHSO3
R) HIO4
S) NaBH4
Which of the following options are correct for following conversion:
(1) 1→S, 2→Q, 3→R, 4→P
(2) 1→Q, 2→R, 3→P, 4→S
(3) 1→Q, 2→P, 3→R, 4→S
(4) 1→P, 2→Q, 3→R, 4→S
14. Which of the following reactions involve hydride ion transfer?
)3 CH3 - C - CH3
15 Mixture of phCHO and HCHO is treated with conc NaOH, then cannizzaro reaction involves (1) reduction of HCHO
(2) oxidation of HCHO
(3) reduction of PhHO (4) oxidation of PhCHO
16. Preparation of benzaldehyde by Etard’s reaction is not from
(1) toluene (2) ethylbenzene
(3) benzoyl chloride (4) sodium benzoate
17. Which of the following gives silver mirror test?
(1) HCOOH (2)CH3COCHOHCH3
(3) tartaric acid (4) glucose
18. Compound (X) C4H8O decolourises Baeyer’s reagent. It undergoes hydrolysis in dil H 2 SO 4 to give (Y) and (Z) where both Y and Z give positive iodoform test while only ‘Y’ responds to Tollens test but (Z) doesn’t. Choose the correct statements of the following:
(1) 3 NaOH YCHCHCHCHO D →−=−
(2) 22 PCC CHCl ZY →
(3)
(4) 32 , otherproduct OHO Zn XY→+
19. Methanoic acid and ethanoic acid can be distinguished by (1) Fehling's solution
(2) Tollens' reagent
(3) FeCl3
(4) Conc. H2SO4
20. In which of the following reactions the predominant product would be 2-pentanone?
(1) OH 3 3 () () iCHMgBr PCC PCC iiHO +
(2) 322 3 () 3 () (excess) iCHCHCHMgBr iiHO CHCN +
(3) 3 3 () 32225 () (excess) iCHMgBr iiHO CHCHCHCOOCH +
(4) CN (excess) (i) CH 3MgBr (ii) H 3O +
Integer Value Questions
21. NaBH 4 can be used to reduce several compounds. Number of compounds that can be reduced by NaBH4 are:
22. If the degree of unsaturation of compound [R] of the following reaction sequence is 2x the value of x is____.
1. NBS / CCl4 (2 eqv)
2. KCN / DMSO (2 eqv )
3. HCl / H2 O (excess)
1. SOCl2 (2 eqv )
2. anhyd. Alcl3
3. H2 O [R] [Q]
23. Which compound among following can give 2,4-DNP test (2,4-dinitrophenylhydrazine)
24. Total number of β-keto monocarboxylic acids (including stereoisomers) which on heating give O Et
25. Find the total number of carboxylic acid groups in the product 'M'
26. Number of compounds that are more acidic than benzoic acid is ______.
Sum of molecular mass of g as (A+C) is X
then calculate 10 X ?
(use: Molar mass (in g.mol−1) of H,C and O as 1,12 and 16, respectively)
30. The total number of stereoisomers for Q CH3CH2CHO + 3HCHO ) 3 (1 . (alcohol) CHCHOeq NaOH H PQD+
31. Observe the following compounds:
27. 2.03 mL of acetone (0.80 g/mL) is mixed with 8.904 mL of benzaldehyde(1 g/mL) to form 0.014 mol of cross aldol-dehydration product with degree of unsaturation, 11. What is the percentage yield of the product? Report answers after dividing with 10. Molecular mass of acetone= 58 u and benzaldehyde=106 u.
28.
The CO2 liberated on heating one mole of above compound when passed over red-hot coke. How many moles of CO is formed
How many compounds g ives faster nucleophilic addition reaction than the below mentioned compound?
32. Reaction-I: O
Reaction-II: Br Br
Reaction-III: Et - CH - CH2
Br
Value of x + y + z is
33. The maximum number of mono aldols (β-Hydroxy carbonyl compounds) can be formed in the following reaction. (Ignore stereoisomers)
34. Acetaldehyde will test positive in how many of the following tests. i) Lucas test ii) Victor Meyer test iii) iodoform test iv)sodium bisulfite test v)litmus test vi) sodium metal test vii) Tollens' test viii) Fehling’s solution test ix) 2,4-DNP test
35. How many compounds (including stereo isomers) with molecular formula C 5 H 10O may be reduced with NaBH 4 to primary alcohol?
Passage-based Questions
Passage 1
Three isomeric compounds (C8H8O) X, Y and Z give the following laboratory tests.
Isomers FeCl3 [Ag(NH3)2]+ Na metal
X Coloured solution Negative Effervescence
Y Negative Precipitate Negative
Z Negative Negative Negative
36. X can be
37. Z can
Passage 2
Diastereomeric products (X)
38. The number of possible isomers of A that can produce diastereomeric products is ‘X’, then value of 2 5 x is _____.
39. If the number of possible structures of A that can give a positive iodoform test is ‘a’ and number of possible structural isomers that give positive Fehling's Test is ‘b’, then value of a b is _____.
Passage 3
An organic compound ‘A’ (C9H8O2) does not decolourises bromine water and evolves no gas with CH3MgBr, but gives orange precipitate with 2, 4 – dinitro phenyl hydrazine. ‘A’ on refluxing with dil. H2SO4 produces B(C9H10O3) then forms salt with NaOH and on treatment with CH 3COCl yields C 13 H 14O 5. B is a nonresolvable compound that on heating with N 2 H 4 /NaOH yields ‘C’ (C 9 H 12 O 2 ). ‘C’ on dehydrating with conc.H 3 PO 4 yields ‘D’ (C9H10O) as major product. ‘D’ on ozonolysis following by work-up with (CH 3 ) 2 S yields ‘E’ (C7H6O2), which can also be obtained by the action of phenol with alkaline solution of chloroform followed by acidification of product.
40. What will be the molecular mass of the product obtained after acidic hydrolysis of the compound C13H14O5 formed in the above passage? (ignore AcOH)
41. What will be the degree of unsaturation of the compound obtained after treating ‘E’ with Tollens' reagent followed by acidification?
Passage 4
Consider given reaction. 2 333 ( 50%) (4mole) NaOHI yield CHCOCH CHCOONa + −−→− y mole Ag powder ) , 3 (yield 1 (P mol 00%) (X mol e e)
Red hot Fe or Cu tube () Compound() ZQ →
and t= degree of unsaturation of compound Q.
42. Value of (X+t) is ……………
43. Value of (y+P) is …………….
Passage 5
Observe the following sequence of reaction and answer the related questions 1) O3 HIO 4 2) Zn / H2 O /
44. Which of the test not given by product 'P'?
(1) Tollen’s reagent
(2) I2/NaOH
(3) 2,4-DNP
(4) Lucas test
45. Number of stereo isomers possible for compound “W” is
(1) 2
(2) 3
(3) 4
(4) 6
Passage 6
An organic compound ‘P’ with molecular formula C8H8O forms an orange red ppt with 2,4-DNP gives yellow precipitate on heating with I 2 in presence of NaOH. It neither
reduces Tollen’s or Fehling reagent nor does it decolourise Br2 water or Baeyer’s reagent. On drastic oxidation with chromic acid (H2CrO4) it gives an acid (Q) having molecular formula C7H6O2. (Use: Molar mass (in g.mol−1) of H,C and O as 1,12 and 16, respectively)
46. NaOH/CaO/ Ä Q R(Major product); →
What is the molecular weight of R?
47.
The number of stereoisomers in the final product T is _____.
Passage 7
An optically inactive compound (A) gives (+) ve iodoform test and gives coloured compound with Braddy’s reagent. When it is treated with hydroxyl amine in mild acidic medium, it produces two different compounds (B) & (C). Each when further heated with conc. H2SO4 produces (D) & (E) respectively. Further, hydrolysis of (D) & (E) both produce mixture of carboxylic acid and an amine. Acid produced by hydrolysis of (D) is most acidic among its isomers and the amine produced by hydrolysis of (E), is least basic among its positional isomers.
48. Identify (A) among the following:
49. Select incorrect statement among the following;
(1) Acid produced by hydrolysis of D will give effervescence of CO 2 with NaHCO3 faster than the acid produced by hydrolysis of E.
(2) Base produced by hydrolysis of D will be more basic than the base produced by hydrolysis of E.
(3) Reaction involves formation of B & C, which can also be carried out with NH2NH2.
(4) Reaction involves formation of D & E, which can also be carried out with PCl5
Passage 8
The aldol condensation also offer a convenient way to synthesize molecules with five and six membered ring. This can be done by intramolecular aldol condensation using a dialdehyde, a keto aldehyde or a diketone as the substrate. The major product is formed by the attack of the enolate from the ketone side of the molecule that adds to the aldehyde group. The reason the aldehyde group undergoes addition preferentially may arise from the greater reactivity of aldehyde towards nunleophilic addition generally. In reaction of this type five membered rings form far more readily than seven membered rings and six membered rings are more favourable than four or eight membered rings when possible.
50. What is the product of 1-Ehtylcyclopent1-ene on reductive ozonolysis followed by heating with aq. NaOH?
51. The product in the below reaction is
Passage 9
In the following reaction sequence, the percentage yield corresponding to the product formed in each step is given in the parenthesis. (Atomic weight (g.mol –1 ): H = 1, C = 12, N = 14, O = 16)
52. The amount of ‘C’ ( in g) formed from 10 moles of toluene is ____.
53. How many of the following compounds are more acidic than ‘A’?
i) Formic acid
ii) 2-Methylbenzoic acid
iii) Acetic acid
iv) 4-Hydroxybenzoic acid
v) 2-Hydroxybenzoic acid
vi) 3-Methoxybenzoic acid
Passage 10
Michael addition of a ketone enolate (or its enamine) to an α, β- unsaturated ketone gives a diketone; diketone undergoes a spontaneous intramolecular aldol condensation known as Robinson annulation (ring forming) reaction.
54. In the given reaction sequence
Which of the following is correct?
In the above two reactions P and Q are, respectively.
Reaction-I
Matrix Matching Questions
56. Match the List-I with List-II.
List-I List-II
(A) cinnamaldehyde (p) 2-hydroxy benzaldehyde
(B) valeraldehyde (q) 3-phenyl prop2-enal
(C) acetophenone (r) pentanal
(D) salicylaldehyde (s) Prop-2-enal (t) 1-phenyl ethanone
(A) (B) (C) (D)
(1) q t r s
(2) q r t p
(3) r q p t
(4) r p q t
10: Aldehydes, Ketones and Carboxylic Acids
57. Match Column-I (Conversion) with Column-II (Reagent).
Column I Column II
(A) Acid chloride to aldehyde (p) DIBAL-H
(B) Benzene to benzaldehyde (q) CO, HCl, anhyd. AlCl3
(C) Acetylene to aldehyde (r) HgSO4, H2SO4
(D) Ester to aldehyde (s) H2, Pd-BaSO4
(A) (B) (C) (D)
(1) s q p r
(2) p q r s
(3) r q p s
(4) s q r p
58. Match List-I with List-II. List-I (Reaction) List-II (Reagents)
(A) Hoffmann Degradation (p) conc. KOH, ∆
(B) Clemenson reduction (q) CHCl3, NaOH/ H3O
(C) Cannizzarro reaction (r) Br2/NaOH
(D) Reimer-Tiemann Reaction (s) Zn-Hg/HCl
(A) (B) (C) (D)
(1) q r p s
(2) r s q p
(3) r s p q
(4) q s p r
59. Match the reagents in column-I with products formed by reactions with acetone in column- II and mark the appropriate choice.
Column-I Column-II
(A) Hydrazine (p) (CH3)2C=NNHCONH2
(B) Semicarbazide (q) (CH3)2C=NOH
(C) Phenyl hydrazine (r) (CH3)2C=NNH2
(D) Hydroxy lamine (s) (CH3)2C=NNHC6H5
(A) (B) (C) (D)
(1) p q r s
(2) s r q p
(3) r p s q
(4) q s p r
60. Match the column-I with Column-II.
Column-I (Acid)
Column-II (pKa value)
(A) HCOOH (p) 1.73
(B) CH3COOH (q) 3.74
(C) PhCOOH (r) 4.17
(D) (COOH)2 (s) 4.75
(A) (B) (C) (D)
(1) q s r p
(2) q s p r
(3) s q r p
(4) r q s p
61. Match the Column-I with Column-II
Column-I (compound) Column-II (eno lcontent)
(A) CH 3 - C - CH 2 - C - OCH 2CH 3 O O (p) 80
(B) Ph C CH3 O (q) 89.2
(C) CH3 - C - CH2 - C - CH3 O O (r) 1.1 10 –6
(D) Ph - C - CH2 - C - CH2 O O CH3 (s) 8.4
(A) (B) (C) (D)
(1) p q r s
(2) s r q p
(3) r s p q
(4) s r p q
BRAIN TEASERS
1. Pheromones are chemicals that animals produce for social response. The structure of brevicomin, a pheromone, is shown below. The open chain ketodiol that would form brevicomin is
(1) 7,8-dihydroxynonan-3-one
(2) 6,7-dihydroxynonan-3-one
(3) 7,8-dihydroxynonan-2-one
(4) 6,7-dihydroxynonan-2-one
2. The major product of the following reaction is: O O (i) dil. HCl/ (ii) (COOH) 2 / Polymerisation CH3 O OH
3. An aromatic compound ‘A‘ having molecular formula C7 H6O2 on treating with aqueous ammonia and heating forms compound ‘B’. The compound ‘B’ on reaction with molecular bromine and potassium hydroxide provides compound ‘C’ having molecular formula C6H7N. The structure of ‘A’ is: (1) COOH (2) O
O
(R = alkyl) R O alkaline KMnO4 strong heat ‘A’ and ‘B’ in the above reaction are:
= alkyl)
(1) R
(2) R O
H = A, B = R
= A, B
R
(4) R O CHO = A, B = R CH3
Passage - 1
An organic compound (A) with molecular formula C10H12O2 on treatment with CH3 I in
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
alkali gives (B) C11H14O2, which is insoluble in aq.NaOH and decolourises Br 2 /CCl 4 . Compound (A) on treatment with strong alkali alone gives an isomeric product (C), which on ozonolysis give (E) C 8 H 8 O 3 , an isomer of isovaniline. (B) on treating with strong base gives (D), which on ozonolysis gives (F) (C9H10O3).
5. The structure of compound (A) is (1)
6. Compounds (E) and (F) are respectively (1)
Passage - 2
Carbonyl compounds which does not contains α hydrogens can undergo Cannizzaro reaction in the presence of strong alkali such as NaOH, KOH etc. In this reaction hydride ion acts as nucleophile.
7. In the following reaction what are the major product formed
(assume exchange reactions are not possible)
(1) D3COH+DCOO–(2) D2HCOH + HCOO–(3) D2COCH + DCOO–(4) DH2COH + DCOO–
8. Which of the following is strong hydride releasing intermediate in the reaction
(1) (2) (3) (4)
FLASH BACK (Previous JEE Questions)
JEE Main
1. The minor product formed in the following reaction is: (2023)
2. Major product P formed in the following reaction is: (2023)
3. The descending order of acidity for the following carboxylic acid is (2023)
A. CH3COOH, B. F3C–COOH
C. ClCH2–COOH D. FCH2–COOH
E. BrCH2–COOH
Choose the correct answer from the options given below: (2023)
(1) B > D > C > E > A
(2) B > C > D > E > A (3) D > B > A > E > C (4) E > D > B > A > C
4. The major product ‘P’ formed in the given reaction is: (2023)
5. In the reaction given below:
H2 N - (i) LiAlH4 (ii) H 2OC 'X' O O
The product 'X' is: (2023)
(1) H2 N OH OH
(2) H2 N OH
(3) H2 N OH O OH
(4) H2 N OH
6. The major product formed in the following reaction is: (2023)
C6H 6 - CH(OH) - CH - CH 2 CHO Zn(Hg) / HCl Major product
CH3 5
(A) C6H 6 - CH(OH) - CH - C2 H5 CH 3 5
(B) C6H 6 - CH = C - C2 H5 CH 3 5
(C) C6 H5 - C = CH - C2H 5
CH3
(D) C6H5 CH3 O
Choose the correct answer from the options given below: (2023)
(1) C only (2) D only
(3) A only (4) B only
7. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R). (2023)
Assertion(A): Cl O can be subjected to Wolff–Kishner reduction to give
Reason (R): Wolff–Kishner reduction is used to convert C CH 2 into O
In light of the above statements, choose the correct answer from the options given below:
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) (A) is false but (R) is true
8. In the following reaction A is (2023)
(i) Mg (ii) H2 O Br 'A' O (Major product)
9. C Me O C CH3 O EtOOEt–
major product A in the above reaction is: (2023)
(1)
CH3
10. The major product ‘P’ formed in the following sequence of reactions is (2023)
(i) SOCl2 (ii) R - NH2 (iii) LiAlH4 (iv) H3 O+ 'P' ( Major product) O OH (1)
11. In the reaction given below. (2023) N Me O (i) NaOH 3 (ii) H + 'A' Major product
(1) MeHN CHO (2) N Me OH (3) MeHN COOH (4) N Me OH OH
O O O 2 HOA(Major)→
‘A’ formed in the above reaction is (2023) (1) O OH OH (2) O OH OH (3) O OH OH O (4) OH O O OH
CHAPTER 10: Aldehydes, Ketones and Carboxylic Acids
13. ‘R’ formed in the following sequence of reactions is (2023)
14. Compound (X) undergoes following sequence of reactions of given the Lactone (Y). (2023)
Compound(X)
Compound
15. Given below are two statements: Statement I: H2 N O Under Clemmensen reduction conditions will give HOOC Statement II : Cl O Under WolffKishner reduction condition will give Cl
In the light of the above statements, choose the correct answer from the options given below: (2023)
(1) Both Statement I and Statement II are true
(2) Statement I is false but Statement II is true
(3) Both Statement I and Statement II are false
(4) Statement I is true but Statement II is false
16. Which will undergo deprotonation most readily in basic medium? (2023)
(1) Both a and c (2) a only (3) b only
(4) c only
17. ? 2 Q P R /\/\/\PhCOOH,PhCHOH →
The correct sequence of reagents for the preparation of Q and R is (2023)
(1) (i) Cr2O3, 770 K, 20 atm (ii) CrO2Cl2, H3O+ (iii) NaOH (iv)H3O+
(2) (i) Mo 2O 3, ∆ (ii) CrO 2Cl 2, H 3O + (iii) NaOH (iv) H3O+
(3) (i) CrO2Cl2, H3O+ (i) Cr2O3, 770 K, 20 atm (iii) NaOH (iv)H3O+
(4) (i) KMnO4, OH– (i) Mo2O3, ∆ (iii) NaOH (iv) H3O+
18. A in the given reaction is (2023) O COOH OH H , H A major + +
(1)
(2) O O O (3) O O OH
(4) C OH O O
19. Among the following the number of compounds which will give positive iodoform reaction is (2023)
a) 1- Phenylbutan-2-one
b) 2-Methylbutan-2-ol
c) 3-Methylbutan-2-ol
d) 1-Phenylethanol
e) 3,3- dimethylbutan-2-one
f) 3-Phenylpropan-2-ol
The value of x in compound ‘D’ is ________ (2023)
21. The mass of NH3 produced when 131.8 kg of cyclohexane carbaldehyde undergoes. Tollen’s test is _____ kg. (nearest integer) Molar Mass of C = 12 g/mol, N = 14 g/mol, O = 16 g/mol (2023)
22. Number of compounds from the following which will not dissolve in cold NaHCO 3 and NaOH solutions but will dissolve in hot NaOH solution is ____ (2023)
23. The number of molecules which gives haloform test among the following molecules is ___. (2023)
JEE Advanced
24. Consider the following reaction scheme and choose the correct option(s) for the major products Q, R and S. (2023)
(ii) NaCN (iii)HO, Ä
25. The major products obtained from the reactions in List-II are the reactants for the named reactions mentioned in List-I. Match List-I with List-II and choose the correct option. (2023)
List I List II (A) Etard reaction (p) Acetophenone
Zn-Hg,HCl →
(B) Gattermann reaction (q) Toulene
4 2 (i) KMnO,KOH, (ii) SOCl D →
(C) GattermannKoch reaction (r) Benzene
3 3 CHCl anhyd. AlCl →
(D) Rosenmund reduction (s) Aniline
2 NaNO/HCl 273-278 K → (t) Phenol Zn, D →
(A) (B) (C) (D)
(1) q s p r
(2) p r t q
(3) r q p s
(4) r s t q
26. In the following reactions, P, Q, R, and S are the major products.
(i) KMnO4, KOH, (ii) H2 O
(i) KMnO4, KOH, (ii) H2 O H3 CH2 C P (i) NaOH, H2 O (ii) H3 O
C P
(i) NaOH, H2 O (ii) H3 O
(i) H 2O (ii) HzCrO4
(i) H 2O , (ii) HzCrO4 (i) Mg. dryether (ii) CO2, then H 3O (iii) Ammoniacal AgNO 3 , H 2O
(i) Mg. dryether (ii) CO2, then H 3O (iii) Ammoniacal AgNO 3 , H 2O
The correct statement(s) about P, Q, R, and S is(are) (2023)
(1) P and Q are monomers of polymers dacron and glyptal, respectively.
(2) P, Q, and R are dicarboxylic acids.
(3) Compounds Q and R are the same.
(4) R does not undergo aldol condensation and S does not undergo Cannizzaro reaction.
27. Choose the correct option(s) for the following reaction sequence. (2019)
i) Hg 2+ , dil, H2 SO4 ii) AgNO 3 , NH4 OH iii) zn-Hg, con. HCl i) SOCl2 pyridine ii)
Consider Q, R and S major products
28. In the following reaction sequence, the amount of D (in g) formed from 10 moles of acetophenone is____. (Atomic weight in g mol–1: H = 1, C = 12, N = 14, O = 16, Br = 80. The yield (%) corresponding to the product in each step is given in the parenthesis) (2018)
CHAPTER TEST – JEE MAINS
Section - A
1. Match List-I with List-II. List-I (Name of reaction) List-II (Reagent used)
(A) Hell -VolhardZelinsky reaction (p) NaOH+I2
(B) Iodoform reaction (q) (i) CrO2 Cl2, CS2 (ii) H2O
(C) Etard reaction (r) (i) Br2/red phosphorus (ii) H2O
(D) GattermanKoch reaction (s) CO, HCl, anhyd. AlCl3
Choose the correct answer from the options given below.
(A) (B) (C) (D)
(1) r q p s (2) r p q s
(3) p q r s (4) r p s q
2. x 33 CHCOClCHCHO → y 3 33 CHCOClCHCOCH →
What are x and y?
(1) Pd−BaSO4/quinoline, (CH3)2Cd
(2) Pd−BaSO4/quinoline, DIBAL-H
(3) DIBAL-H, LiAlH4 (4) DIBAL-H, (CH3)2Cd
3. Which of the following reagents/reactions will convert A to B? CH 2 H 3C H3 C CHO (A) (B)
(1) PCC oxidation
(2) ozonolysis
(3) BH 3 , H 2 O 2 /OH followed by PCC oxidation.
(4) HBr, hydrolysis followed by oxidation by K2Cr2O7
4. Two isomers 'A' and 'B' with molecular formula C 4 H 8 give different products on oxidation with KMnO 4 in acidic medium. Isomer ‘A’ on reaction with KMnO 4 /H + results in effervescence of a gas and gives ketone. The compound ‘A’ is (1) But-1-ene. (2) cis-But-2-ene.
(3) trans-But-2-ene. (4) 2-Methylpropene.
5. X 32 32 CHCHCNCHCHCHO → Y 222 CHCHCHOHCH=CHCHO = → + 1.Z 32 322 2.H CHCHCHOCHCHCHOH →
Identify reagents (X),(Y),(Z). X Y Z
(1) DIBAL-H LiAlH 4 PCC
(2) DIBAL-H PCC LiAlH 4
(3) LiAlH 4 PCC DIBAL-H
(4) PCC LiAlH 4 DIBAL-H
6. The major product 'P' for the following sequence of reactions is: Ph OH OH NH 2 1) Zn/Hg HCl 2)LiAlH4 3)H3O+ 'P' majorproduct
(1) Ph OH OH NH 2
(2) Ph OH OH
(3) Ph NH2
(4) Ph OH NH2 7 2 i) Ba(OH) Acetone X D →
(1) 4-Methyl pent-3-ene-2-one (2) 3-Methyl pent-3-ene-2-one
(3) Hex-3-ene-2-one (4) Pent-3-ene-2-one
NaBH4 H2 Pd CH = CH - CHO B A A and B are respectively (1) CH 2 - CH2 - CHO CH = CH - CH 2 - OH , (2) CH2 - CH 2 - OH CH = CH - CH , CH2OH, CH2OH (3) CH = CH - CH2 - OH in both cases (4) CH 2 - CH2 - CH 2 - OH in both cases 9. O NH 2OH H + IAH H 2O (A) (B) (C) () LAH C → Product (C ) of the reaction is :
10. Rank the following in order of increasing value of the equilibrium constant for hydration Khyd (smallest value first).
12. Which of the following compound/s are not involved inCannizaro reactions? (1)
(2)
(1) (2) (3) (1) 1 < 2 < 3 (2) 3 < 1 < 2 (3) 2 < 1 < 3 (4) 2 < 3 < 1
11. The products formed in the following reaction, A and B are O
13. I n the Cannizaro reaction given below.– OH 22 2PhCHOPhCHOH+PhCO → The slowest step is
(1) The attack of OH– at the carbonyl group
(2) The transfer of hydride to the carbonyl group
(3) The abstraction of proton from the carboxylic group
(4) Deprotonation of PhCH2OH
14. The increasing order of the reactivity of the following compounds in nucleophilic addition reaction is : propanal, benzaldehyde, propanone, butanone
(1) benzaldehyde>butanone< propanone < propanal
(2) butanone< propanone < benzaldehyde < propanal
(3) benzaldehyde< propanal < propanone < butanone
(4) propanal< propanone < bu tanone < benzaldehyde
Cl2 h Alc.KOH KMnO4 H+ A B C /
(1) Malonic acid
(2) Adipic acid
(3) Maleic acid
(4) Succinic acid
16. Hydrolysis of an ester gives a carboxylic acid, which on Kolbe’s electrolysis yields ethane. The ester is
(1) Methyl ethanoate
(2) Methyl methanoate
(3) Ethyl methanoate
(4) Methyl propanoate
17. Which of the following reactions gives acetamide?
(1) Hydrolysis of CH3CH2CH2CN
(2) Heating CH3COOH with NH3 followed by further heating
(3) Reaction of CH 3CH 2CN with LiAlH 4 followed by H2O
(4) CH3CN with NaHg/C2H5OH
18. Major product of nitration of benzoic acid is
(1) 3 - nitrobenzoic acid
(2) 2 - nitrobenzoic acid
(3) 2, 4 - dinitrobenzoic acid
(4) 4 - nitrobenzoic acid
19. The major product of the following reaction is:
20. Benzoic acid is not a product in
Section-B
21. The total number of compounds (shown below) that form phenylhydrazone derivatives under acidic conditions is ____.
24 4 dil.HSO 3 HgSO (4.0 g) 80%
The mass of “C” formed in this reaction is
23.
X = Number of compound obtained by Aldol reaction
Y = Number of compounds react with NaHCO3
Sum of X + Y is______
24. A carbonyl compound of formula C9H10O(A), which is a benzene derivative gives orange precipitate with 2, 4-D.N.P and also gives yellow precipitate with I 2 in presence of aqueous NaOH. The total no. of isomers possible for A are ____.
CHAPTER TEST – JEE ADVANCED
2023 P1 Model
Section-A
[Single Option correct MCQ's]
1. Compound ‘A’ is dibasic acid HOOC–(CH2)5-COOH
25. How many number of the following compounds will liberate CO 2 when treated with NaHCO3
Find the major product of the reaction is:
Compound E is
3. An organic compound 'X' having molecular formula C5H10O yields phenyl hydrazone and gives negative response to the iodoform test and Tollens' test. It produces n-pentane on reduction. 'X' could be:
(1) 2-Pentanone (2) 3-Pentanone
(3) n-Amylalcohol (4) Pentanal
Section-B
[Multiple Option Correct MCQs]
4. CH3 C CH3 CH3 C O Ag Br2 O Major product
(1) C CH3 CH3 CH3 CH2 Br (2) C CH3 CH3 CH3 Br
(3) CH 3 H2 C = C CH3 (4) C CH3 CH3 CH3 C CH3 CH3 CH3
5. How many β-keto Acids will easily undergo decarboxylation? (1) OH
6. With reference the scheme given, which of the given statement(s) about T, U, V, and W is/are correct O C H3 C O T U W V LiAlH4 excess (CH 3CO)2 O CrO3/H +
(1) 'T' is soluble in hot aq NaOH.
(2) ‘U’ is optically active.
(3) Molecular formula of W is C 10 H18O4.
(4) V gives effervescence with aq NaHCO3. 7. O - C - CH3 O AlCl3 (anhydrous) CS2 , 100o C A major B minor +
Which of the following statement(s) are true?
(1) Reaction involves the attack of acylium carbocation at ortho and para positions of benzene ring
(2) Products A and B gives violet colour with FeCl3
(3) A and B mixture can be separated by steam distillation in which A is collected as distillate
(4) A and B mixture can be separated by steam distillation in which B is collected as distillate
Section-C
[Integer Value Questions]
8. If (dl) or (±) 2-methyl butanoic acid were esterified by reaction with (dl) or
(±) 2-butanol, how many optically active compounds would be present in the final equilibrium reaction mixture?
9. Benzaldehyde when treated with catalytic amount of CN , major product 'p' is formed. What is the number of π-bonds in one molecule of the product ‘p’?
10. How many of the following acids will show higher reactivity towards esterification reaction as compared to acetic a cid?
11. The maximum number of moles of Grignard reagent will be consumed per mole of following compound?
Questions]
12. Consider the reaction given below:
The number of chiral carbon atoms in the compound obtained by the reduction of the major product, U, using H 2/Ni is ______.
13. The number of pi bonds in compound [Z] is
14. The number of sp 3 carbon atoms present in the product E is _____.
15. The number of π-bonds present in the product G is ______
Passage
For the following reaction scheme, percentage yields are given along the arrow.
hot Irontube, 873k
x and y are the masses of R and U, respectively (use: Molar mass (in g.mol −1) of H,C, and O as 1,12 ,and 16 respectively.
16. The value of x is ______.
17. The molecular weight of S is ____.
- II
Level - III
Theory-Based Questions
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Chapter Test – JEE Mains
Chapter Test – JEE Advanced
