Valori pka composti organici parte 1

pKa Data Compiled by R. Williams

page-1 pKa Values

INDEX Inorganic 2 Phenazine Phosphates 3 Pyridine Carboxylic acids 4, 8 Pyrazine Aliphatic 4, 8 Aromatic 7, 8 Quinoline Phenols 9 Quinazoline Alcohols and oxygen acids 10, 11 Quinoxaline Amino Acids 12 Special Nitrogen Compounds Peptides 13 Hydroxylamines Nitrogen Compounds 14 Hydrazines Aliphatic amines 15, 17, 19 Semicarbazones Cyanoamines 16 Amidoximes Anilines 17, 18, 20 Thiols Nucleosides 21 Carbon Acids Special Table Heterocycles 22 Indicators Acridine 23 References Benzoquinoline 24 Cinnoline 23 Hydantoin 24 Imidazole 24 For complex chelating agents, see also reference 77.

24 25 26 27 27 27 28 28 28 28 28 29 30,31 31 32-34

Note. This document was compiled by W.P. Jencks and has been added to by F.H. Westheimer

pKa Data Compiled by R. Williams ACIDS

Compound AgOH Al(OH)3 As(OH)3 H3 AsO4 H2 AsO4 – HAsO 4 * As 2 O3 H3 AsO3 H3 BO 3 H2 B4 O7 HB4 O7 Be(OH) 2 HBr HOBr HOCl HClO2 HClO3 HClO4 (70%) CH3 SO 3 H HCN H2 CO 3 HCO3 H2 CrO4 HCrO4 HOCN HZ H2 GeO3 Ge(OH)4 HI HOI HIO3 H4 IO6 – H5 IO6 HMnO4 NH3 OH* NH4 * HN3 HNO2 HNO3 N2 H5 + H2 N2 O2 H2 N2 O2 – H2 OsO5 H2 O H3 O+ Pb(OH)2

pK 3.96 11.2 9.22 2.22, 7.0, 13.0 6.98* 11.53* 0 9.22* 9.23* 4.00 9.00 3.7 -9.00 8.7 7.53, 7.46 2.0 -1.00 -10.00 -0.6 9.40 6.37, 6.35*, 3.58 10.33* -0.98 6.50* 3.92 3.17*, 0.59* 8.59, 12.72 8.68, 12.7 -10.0 11.0 0.8 6.00 1.64, 1.55, 8.27 -2.25 5.98* 9.24* 4.72* 3.29 -1.3 7.99* 7.05 11.0 12.1 15.7 -1.7 6.48 (10.92)

Ref. 4 28 28 28 77 77 4 28 34 34 4 31 28 28, 33 28 28 31 31 34 34, 32 30 2, 30 34 77 34, 78 28 31 28 28 34 34, 28 30 77 77 28 28 77 34 34 34 none none 4 (78)

page-2 H3 PO 2 H2 PO 4 – HPO 4 _ H3 PO 3 H2 PO 3 – H4 P2 O7 H3 P 2 O7 – H2 P2 O7 = HP2 O7 = HReO4 HSCN H2 SeO3 HSeO3 H2 SeO4 HSeO4 H3 SiO3 H2 SO 3 H2 SO 4 HSO3 HSO4 – H2 S2 O4 H2 Se HSe– H2 S HS– HSbO2 HTe H2 Te H2 TeO3 Te(OH) 6 H2 VO4 – HVO4 = H2 CrO4 HOCN HSCN H3 PO 2 H3 PO 4 H2 S2 O3 H3 AuO3 H3 GaO3 H5 IO6 H4 V6 O17 H2 NSO3 H

2.0, 2.23* 7.21* 12.32* 2.0 6.58* 1.52* 2.36* 6.60* 9.25* -1.25 4.00 2.6, 8.3, 2.62* 8.32 Strong, 2.0 2.00 10.0 1.9, 7.0, 1.76* -3.0, 1.9 7.21* 1.99* 1.9 3.89* 11.00* 7.00* 12.92* 11.0 5.00 2.64, 11.0 2.7, 8.0 6.2, 8.8 8.95 14.4 0.74 3.73 0.85 1.07 2.12* 0.60*, 1.72* 13.3, 16.0 10.32, 11.7 3.29, 6.70, 15.0 (see above!)

1.96 1.0

* Indicates a thermodynamic value.

28 77 77 28 77 77 77 77 77 30 34 28 77 28 34 34 28, 77 28 77 77 29 77 77 77 77 34 34 34, 78 28 28 30 30 77 77 77 77 77 77 78 78 78 78 80

PHOSPHATES AND PHOSPHONATES

Phosphates Compound

pK

Phosphate 1.97, 6.82, 12.5 Glyceric acid 2-phosphate 3.6, 7.1 Enolpyruvic acid 3.5, 6.4 Methyl1.54, 6.31 Ethyl1.60, 6.62 n-Propyl1.88,6.67 n-Butyl1.80, 6.84 Dimethyl1.29 Di-n-propyl 1.59 Di-n-butyl1.72 Glucose-30.84, 5.67 Glucose-40.84, 5.67 α -glycero1.40, 6.44 β-glycero1.37, 6.34 3-phosphoglyceric acid 1.42, 3.42 2-phosphoglyceric acid 1.42, 3.55, 7.1 peroxymonophosphoric acid 4.05 diphosphoglyceric acid 7.40, 7.99 glyceraldehyde2.10, 6.75 dioxyacetone1.77,6.45 hexose di1.52, 6.31 fructose-60.97, 6.11 glucose-60.94, 6.11 glucose-11.10, 6.13 adenylic acid 3.8?, 6.2? inosinic acid 2.4?, 6.4?

ADP 2 strong, 6.6 ATP 3 strong, 6.6 pyrophosphoric acid 0.9, 2.0, 6.6, 9.4 phosphopyruvic acid 3.5, 6.38 creatine phosphate 2.7, 4.5 arginine phosphate 2.8, 4.5, 9.6, 11.2 arginine 2.02, 9.0, 12.5 amino phosphate (-0.9), 2.8, 8.2 trimetaphosphate 2.05

Ref.

55 53 53 55 55 55 55 55 55 55 56 56 54 54 54

69 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 77

Phosphonates H 2O3P(CH2) 4PO3H 2 <2, 2.75, 7.54, 8.38 57 H 2O3P(CH2) 3PO3H 2 <2, 2.65, 7.34, 8.35 57 H 2O3PCH 2CH(CH3)PO 3H 2 <2, 2.6, 7.00, 9.27 57 H 2O3PCH 2PO3H 2 <2, 2.57, 6.87, 10.33 57 Methyl2.35 57 Ethyl2.43 57 n-propyl2.45 57 isopropyl2.55, 7.75 57 n-butyl2.59, 8.19 57 isobutyl2.70, 8.43 57 s-butyl2.74, 8.48 57 t-butyl2.79, 8.88 57 neopentyl2.84, 8.65 57 1,1 Dimethylpropyl2.88, 8.96 57 n-hexyl2.6, 7.9 57 n-dodecyl--, 8.25 57 CH 3(CH2) 5CH(COOH)- 1, -57

CF3CCl 3NH 3+CH 2( –OOCCH 2) 2NH +CH 2– CHCl2CH 2CICH 2Br( –OOCCH 22NH +(CH2) 2CH 2INH 3+CH 2CH 2C6H 5CH=CHHOCH2C6H 5NH 2+(CH2) 3C6H 5NH(CH 2) 3Br(CH2) 2CH 3(CH2) 5CH(COO–)C6H 5CH 2NH 3+(CH2) 4)NH 3+(CH2) 5NH 3+(CH2) 10–OOC(CH2) 10(CH3) 3SiCH 2C6H 5CH 2(C 6H 5)SC-

1.16, 3.93 1.63, 4.81 2.35, 5.9 --, 5.57 1.14, 5.61 1.40, 6.30 1.14, 6.52 --, 6.54 1.30, 6.72 2.45, 7.00 2.00, 7.1 1.91, 7.15 2.1, ---, 7.17 2.25, 7.3 --, 7.5 2.3, 7.55 2.55, 7.55 2.6, 7.6 --, 8.00 --, 8.25 3.22, 8.70 3.3, 8.4 3.85, 9.00

57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57

Arylphosphonic acids 2X-RC6H 3PO3H 2 X R Cl 4-O 2N Br 5-O 2N Cl 5-Cl Cl H Br H Br 5-CH3 Cl 4-NH 2 CH 3O 4-O 2N CH 3O H CH 3O 4-O 2N HO 4-O 2N O 2N H F H I H NH 2H --, 7.29 CH 3H 2.10, 7.68 C6H 5 H HOOC H

1.12, 6.14 (a), 6.14 (a), 6.63 1.63, 6.98 1.64, 7.00 1.81, 7.15 --, 7.33 1.53, 6.96 2.16, 7.77 --, 8.22 1.22, 5.39 1.45, 6.74 1.64, 6.80 1.74, 7.06 57 57 (a), 8.13 1.71, 9.17

57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57

**These values were obtained in 50% ethanol. (a) The compounds were not sufficiently soluble.

For graphical plots of a large number of substituted phosphorus compounds see 83. triphosphate 8.90, 6.26, 2.30 77 tetrametaphosphate 2.74 77

fluorophosphate 0.55, 4.8 56 Phosphonates (Ref. 2) X -H -H -NH 3+ -NH 3+ X(CH2)PO 3H 2 2.35 7.1 1.85 5.35 X(CH2) 2PO3H 2 2.45 7.85 2.45 7.00 X(CH2) 4PO3H 2 2.55 7.55 X(CH2) 5PO3 H2 2.6 7.65 X(CH2) 6PO2H 2 2.6 7.9 X(CH2) 10PO2H 2 8.00 Phosphines in acetonitrile, see ref. 89.

CARBOXYLIC ACIDS Aliphatic Compound pK Acetoacetic 3.58 Acetopyruvic 2.61, 7.85 (enol) Aconitic, trans2.80, 4.46 Betaine 1.84 Citric 3.09, 4.75, 5.41 Crotonic 4.69 Dihydroxyfumaric 1.14 Dethylenediamine- 2.00, 2.67 tetraacetic 6.16, 10.26 Formic 3.77* Fumaric 3.03, 4.54 Glyceric 3.55 Glycollic 3.82 Glyoxylic 3.32 Homogentistic 4.40 α -keto-β -methyl valeric 2.3 Lactic 3.86 Maleic 1.93, 6.58 Malic 3.40, 5.2 Oxaloacetic (trans-enol) 2.56 +(cis-enol) 2.15, 4.06 Protocatechuic 4.48 Pyruvic 2.50 Tartaric + 2.99, 4.40 + or 2.89, 4.40 meso 3.22, 4.85 Vinylacetic 4.42

Ref. 6 6 6 6 6 6 6 6 2 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

Acetic acids, substituted H4.76* O2N1.68* (CH3)3N+1.83* + (CH3)2NH 1.95* + 2.16* CH3NH2 NH3+2.31* CH3SO22.36* NC2.43* C6H5SO22.44 HO2C 2.83* C6H5SO2.66 F2.66 Cl2.86* Br2.86 Cl21.29 F 21.24 Br30.66 Cl30.65 F 30.23 (-0.26) (2) HONC4 3.01 F3C3.07* N 33.03 I3.12 C6H5O3.12 C2H5O2C3.35 C6H5S3.52* CH3O3.53 NCS3.58 CH3CO3.58* C2H5O3.60 n-C3H7O 3.65 n-C4H9O 3.66 sec.-C4H9O3.67 HS3.67* i-C3H7O3.69* CH3S3.72* i-C3H7S3.72* C6H5CH2S3.73* C2H5S3.74* n-C3H7S3.77* n-C4H9S3.81* HO3.83* –O3S4.05 (C6H5)3CS4.30* C6H54.31* CH2-CH4.35* * Indicates thermodynamic values.

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

Unsaturated acids (25°) Compound pK trans-CH 3-CH=CHCO 2H 4.69* cis-CH3-CH=CHCO 2H 4.44* C6H5-CH2CH2CO2H 4.66* trans-C 6H5-CH=CHCO 2H 4.44* m-CH 3OC6H4CH2CH2CO2H 2 m-CH 3OC6H4CH=CHCO 2H 4.38* m-ClC 6H4CH2CH2CO2H 4.58*

ref.

20 2 2 2 4.65*

Compound H-CH2CH2CO2H H-CH=CHCO 2H C6H5CH2CH2CO2H C6H5CH=CHCO 2H** C6H5CH2CH2CO2H C6H5CH=CHCO 2H** m-ClC 6H4CH=CHCO 2H**

2 2

pK 4.88* 4.25* 4.66* 4.44* 4.66* 4.44 4.29*

ref.

2 2 2 2 2 2 2

Unsaturated acids, Cis- and Trans

R1

R2

cis-acid

HH4.25* CH3H4.44* ClH3.32 C6H5H3.88* ClC6H4 H3.91 6-BrC6H4 H4.02 CH3CH34.30 C6H5H5.26*** 2,4,6-(CH3)3C6H2- H6.12*** C6H5CH34.98*** Dicarboxylic acids, unsaturated* Maleic 1.92, 6.23 2 Citraconic (Dimethylmaleic acid) 2.29, 6.15 2 Acetylenedicarboxylic 1.73, 4.40 2 â&#x2C6;&#x2020;1-tetrahydrophthalic 3.01, 5.34 2 Bromomaleic 1.45, 4.62 2 Bromofumaric 1.46, 3.57 2 Chlorofumaric 1.78, 3.81 2 Fumaric 3.02, 4.38 2 Mesaconic (Dimethylfumaric acid) 3.09, 4.75 2 Phthalic 2.95, 5.41 2 Itaconic (1-Propene-2-3-dicarboxylic acid) 3.85, 5.45 2 Chloromaleic 1.72, 3.86 2

trans-acid

Ref.

4.25* 4.69* 3.65 4.44* 4.41 4.41 5.02 5.58*** 5.70*** 5.98***

2 2 2 2 2 2 2 2 2 2

Alicyclic Dicarboxylic acids cis-Caronic(1,1-dimethylcyclopropane-23dicarboxylic acid 2.34*, 8.31* 2 1,2-trans-cyclopropanedicarboxylic 3.65*, 5.13* 2 trans-caronic 3.82*, 5.32* 2 1,2-cis-cyclopropane-dicarboxylic 3.33*, 6.47* 2 **trans ***in 40% acetone *thermodynamic

Aliphatic Alicyclic Dicarboxylic acids Compound 1,2-trans-Cyclopropanedicarboxylic trans-Ethyleneoxidedicarboxylic 1,3-trans -Cyclobutanedicarboxylic 1,2-trans-Cyyclopentanedicarboxylic 1,3-trans-Cyclopentanedicarboxylic 1,2-trans-Cyclohexanedicarboxylic 1,3-trans-Cyclohexanedicarboxylic 1,4-trans-Cyclohexanedicarboxylic

pK 3.65, 5.13 1.93, 3.25 3.81, 5.28 3.89, 5.91 4.40, 5.45 4.18, 5.93 4.31, 5.73 4.18, 5.42

Dicarboxylic acids* oxalic 1.23, 4.19 Malonic 2.83, 5.69 Methyl3.05, 5.76 Ethyl2.99, 5.83 n-propyl 3.00, 5.84 i-propyl2.94, 5.88 Dimethyl3.17, 6.06 Methylethyl2.86, 6.41 2 Diethyl2.21, 7.29 Ethyl-n-propyl2.15, 7.43 Di-n-propyl2.07, 7.51 Glutaric 4.34, 5.42 B-Methyl 4.25, 6.22 B-Ethyl 4.29, 6.33 B-n-Propyl 4.31, 6.39 B,B-Dimethyl3.70, 6.29 B,B-Methylethyl3.62, 6.70 B,B-Diethyl3.62, 7.12 B,B-Di-n-propyl 3.69, 7.31 D-Tartaric 3.03, 4.45 DL-Tartaric 3.03, ---meso-Tartaric 3.29, 4.92

Ref Compound cis-Ethyleneoxide2 dicarboxylic 1,3-cis-Cyclobutane2 dicarboxylic 1,2-cis-Cyclopentane2 dicarboxylic 1,3-cis-Cyclopentane 2 dicarboxylic 1,2-cisCyclohexane2 dicarboxylic 1,3 -cis-Cyclohexane2 dicarboxylic 1,4-cis-Cyclohexane 2 di-carboxylic 2

pK 1.94, 3.92 4.03, 5.31 4.37, 6.51 4.23, 5.53 4.34, 6.76 4.10, 5.46 4.44, 5.79

2 Succinic 4.19, 5.48 ’ 2 O-O -Dimethyl3.77, 5.94 2 (high melting) 2 O-O’-Dimethyl3.94, 6.20 2 (low melting) 2 O,O’-Diethyl3.63, 6.46 2 (high melting) O,O’-Diethyl3.51, 6.60 2 2 (low melting) 2 Tetramethyl3.50, 7.28 2 2 2 Adipic 4.42, 5.41 2 Pimelic 4.48, 5.42 2 Suberic 4.52, 5.40 2 Azelaic 4.55, 5.41 2 DL-1:2-Dichlorosuccinic 1.68, 3.18 2 meso-1:2-Dichlorosuccinic 1.74, 3.24 2 DL-1:2-Dibromosuccinic 1.48, ---2 meso-1:2-Dibromosuccinic 1.42, 2.97 20 DL-1:2-Dimethylsuccinic 3.93, 6.00 20 meso-1:2-Dimethylsuccinic 3.77, 5.36 20

Ref 2 2 2 2 2 2 2

2 2 2 2

2 2 2 2 20 20 20 20 20 20

*All are thermodynamic values

Aliphatic Bicyclo[2.2.2]octane-1-carboxylic acids, 4substituted H6.75 2 C2H5O2C6.31 2 NC5.90 2

HO6.33 Br6.08 Lysergic acid, etc. ergometrine 6.8, -Dihydroergometrine 7.4, -β -dihydrolysergol 8.2, --

2 2 2 2 2

Lysergic acid

7.8, 3.3 8.3, 3.6 7.3, -8.3, -8.85, -8.4, 3.4 8.6, 3.6

α -dihydrolysergic

ergometrinine α -dihydrolysergol 6-methylergoline isolysergic acid γ-dihydrolysergic

2 2 2 2 2 2 2

C6H5OCH3(CH3)2CH(CH3)3N+NCHO2C* F3CHOICl(CH3)3SiC2H5Oi-C3H7On-C5H11OC6H5CH3CH2(CH3)3C–HO3P–O3SH2N(CH3)2N–HO3As–O2CCH3NH-

Hydroxycyclohexanecarboxylic acids Cyclohexanecarboxylic 4.90 2 cis-1,2 4.80 2 cis-1,3 4.60 2 cis-1,4 4.84 2 trans-1,2 4.68 2 trans-1,3 4.82 2 trans-1,4 4.68 2 Aromatic benzene-CO3H 4.20* 2 Anthracene-1-COOH 3.69 2 Anthracene-9-COOH 3.65 2 naphthalene-2-COOH 4.17 2 Naphthalene-1-COOH 3.69 2 Substituted benzoic acids (ref. 2)

Position of carboxyl 1 1,2 1,3 1,4 1,2,3 1,2,4

3.95* 4.24*

1.37

3.45 3.60* 3.54 3.79 4.08* 3.86* 3.83* 4.24* 4.17* 4.15*

2.95* 2.98* 2.85* 2.94* 4.21* 4.24* 3.46* 3.77 3.46 3.78 4.98 8.42

4.28 4.03 4.15 4.79 5.10

5.41** 5.3

4.60 5.10

4.52* 4.34* 4.35* 3.43 3.55* 3.51 4.58* 3.99* 4.27* 4.45* 4.68* 4.55* 4.35* 4.40* 3.95 4.11 4.92 5.03 4.22 4.82 5.04

*thermodynamic for complex chelating agents, see also ref. 84. see also page 9a for more carboxylic acids.

Ortho-substituted benzoic acids Benzoic acid pK Ref. 2-CH33.91** 2 2-t-C 4H93.46 2 2,6-(CH3)23.21 2 2,3,4,6-(CH3)44.00 2 2,3,5,6-(CH3)43.52 2 2-C2H53.77 2 2-C6H53.46** 2 2,4,6-(CH3)33.43 2 2,3,4,5-(CH3)44.22 2

Benzoic acid o m p H4.20* 4.21* O2N2.17* 3.45* 3.44 CH3COCH3SO23.64* 3.52* CH3SHSBr2.85* 3.81* 4.00* F3.27* 3.87* 4.14* CH3O4.09* 4.09* 4.47* n-C3H7O4.24* 4.20* 4.46* n-C4H9O4.25* 4.53* Benzene Polycarboxylic acids Ref. 2 Acid Benzoic Phthalic Isophthalic Terephthalic Hemimellitic Trimellitic

3.53* 3.91*

pKI 4.17* 2.98* 3.46* 3.51* 2.80* 2.52*

pKII

pKIII pKIV pKV pKVI

5.28* 4.46* 4.82* 4.20* 3.84*

5.87* 5.20*

Trimesic Mellophanic Prehnitic Pyromellitic Benzenepentacarboxylic Mellitic

*ionic strength 0.03 **thermodynamic

1,3,5 1,2,3,4 1,2,3,5 1,2,4,5 1,2,3,4,5 1.2,3,4,5,6

Carboxylic Acids Ref. 77 Aminomalonic acid* 3.32, 9.83 N-Butylaminoacetic acid 2.29, 10.07 2-carboxyethyliminodiacetic acid 2.06, 3.69, 9.66 β -carboxymethylaminopropionic 3.61, 9.46 α ,α -diaminobutyric 1.85, 8.24, 10.44 Di-(carboxymethyl)-aminomethyl phosphonic acid 2.00, 2.25, 5.57, 10.76 α ,β -dimercaptosuccinic 2.40, 3.46, 9.44, 11.82 Ethylenediamine-N,N-diacetic 5.58, 11.05 α -hydroxybutyric 3.65 N-2-hydroxyethyliminodiacetic 2.2, 8.73 3-hydroxypropyliminodiacetic 2.06, 9.24 Iminodipropionic 4.11, 9.61 Isobutyric* 4.86 Mandelic acid 3.41 2-Mercaptoethyliminodiacetic -2.14, 8.17, 10.79 Methyliminodiacetic 2.81, 10.18

3.12* 2.06* 2.38* 1.92* 1.80* 1.40*

8

3.89* 4.70* 3.25* 4.73* 6.21* 3.51* 4.44* 5.81* 2.87* 4.49* 5.63* 2.73* 3.97* 5.25* 6.46* 2.19* 3.31* 4.78* 5.89* 6.96* 2-Methoxyethyliminodiacetic 2.2, 8.96 2-Methylthioethyliminodiacetic 2.1, 8.91 oxalic acid* 1.25, 4.14 N-n-propylaminoacetic 2.25, 10.03 N-2-sulfoethyliminodiacetic 1.92, 2.28, 8.16 α -Bromobutyric acid 2.97 N-(carbamoylmethyl)-imino-diacetic acid 2.30, 6.60 Cyanomethyliminodiacetic 3.06, 4.34 α ,β -diaminopropionic acid 1.23, 6.69 Diethylaminoacetic 2.04, 10.47 Dimethylaminoacetic 2.08, 9.80 N-ethylaminoacetic 2.30, 10.10 Gluconic* 3.86 β -hydroxybutyric 4.39 β -hydroxypropionic 3.73 Iminodiacetic* 2.98, 9.89 β -iodopropionic* 4.04 N-isopropylaminoacetic 2.36, 10.06 α -mercaptobutyric 3.53 N-methylaminoacetic 2.24, 10.01 Nitrilotriacetic 3.03, 3.07, 10.

2-Phosphonoethyliminodiacetic 1.95, 2.45, 6.54, 10.46 *Thermodynamic

PHENOLS Compound Chromotropic acid o-Methoxyphenol o-Hydroxybenzaldehyde 2-Amino-4,5 dimethylphenol hydrochloride 4,5-dihydroxybenzene1,3 disulphonic acid 7.66 Kojic acid Phenol H(CH3 )3 N+CH3 SO 2 CH3 COC2 H5 O2 CC3 H5 CH2 O2 CBrFHOCH3 CH3 O-O2 C-- O3 PC6 H5 2-Chloro-4-Nitro2-Nitro-4-Chloro* Thermodynamic **Reference 52

pK 5.36, 15.6 --, 9.93 7.95 10.4 5.28 12.6e 9.40 o m 9.95* 9.94* 7.42 8 9.33 9.19

Ref. 6 50 50 51 77 p

8 7.83 8.05 8.50* 8.41* 8.42* 9.11* 9.34* 8.81* 9.28* 9.95* 9.48 9.44 9.96 10.28*10.08 10.19* 9.93 9.65 10.20 9.94* 9.39* 10.2 9.9 9.93 9.59 9.51 5.42 79 6.46 79

Compound pK Ref. Resorcinol --, 9.15 (30o) 50 p-Methoxyphenol --, 10.16 50 3-Hydroxyanthranilic acid 10.09, 5.20 51 2-Aminophenol hydrochloride 9.99, 4.86 51

Phenol O2 NOCHNCCH3 O2 Cn-C4 H9 O2 CIClCH3 SHOCH2 C2 H5 H2 N-O3 S-- O3 As NO-

o m p 7.23* 8.35* 7.14* 6.79 8.00 7.66 8.61**7.95 8.47* 8.47* 9.17* 8.48* 9.02* 9.38* 9.53 9.53 9.92* 9.83* 9.82* 10.2 9.9 10.0 9.71 9.87 10.30 9.29 9.03 6.35**

8.37