Chemistry
185
colored easily, electrically insulator, light in weight, easy to carry, durable and not damaged by weather. Although plastic materials have wide advantages but there are some disadvantages too. The main problem of using artificial polymer or plastic is that it is not dissociate and pollute the environment. Most of the natural elements decompose by the bacteria of the soil, but plastic products do not decompose by bacteria. That is why plastic is called non biodegradable substance. In many cases plastics are destroyed by burning by which toxic gases produce (hydrogen chloride, aldehyde, hydrogen cyanide). These gases are carcinogenic and cause other diseases to human. Now scientist produce synthetic polymer which decomposes initially by sunlight (photo-degradable) and then decomposes naturally by bacteria (bio-degradable). This polymer is known as biopolymer. Most of the biopolymer is prepared from sugarcane and corn. This polymer needs 20-30 years to decompose by the bacteria. Polyethanol {-CH2-CH(OH)-}n is one type of polymer which is used in hospital and dissolves in water. Solubility of polyethanol depends on the value of ‘n’. Plastic polymers are prepared from the monomers that are collected from fossil fuel. As a result the stock of limited fossil fuel is decreased. On the other hand the electricity produced from the 4% of total fossil fuel is used in manufacturing plastic products. The demand on the fossil fuel can be decreased by recycling the plastic and not using the unnecessary plastic. It is necessary to decrease the dependency on the synthetic fiber to maintain the balance of environment. Use of natural fiber can be increased including cotton, wool and jute. The land of Bangladesh is fertile, so the use of synthetic fiber can be decrease by cultivating mesta along with cotton and jute. Philippine and Indonesia spin cloths with improved yearn obtained from the leaves of pineapple and fiber of banana trees. 11.6 The preparation of alcohol, aldehyde and organic acid from hydrocarbon The main constituent of petroleum is hydrocarbon (alkane, alkene and alkyne). All kinds of organic compounds are prepared from hydrocarbons. Saturated hydrocarbon or alkane reacts with halogens and produce alkylhalide. Alkene reacts with hydrogen bromide and produce alkyl bromide. Alkyl halides react with aqueous solution of sodium hydroxide and converts to alcohols. If produced alcohol is oxidized by strong oxidant (K2Cr2O7 and H2SO4) produce firstly aldehyde/ketone and later on converts to organic acid. R-CH2-CH3 + Br2 R-CH2-CH2Br + HBr R= alkyl radical -CH3, -C2H5, -C3H7 etc R-CH=CH2 + HBr R-CH2-CH2-Br R-CH2-CH2-Br + NaOH(aq) R-CH2-CH2-OH +NaBr R-CH2-CH2-OH + [O] R-CH2-CHO R-CH2-CHO + [O] R-CH2-COOH