Question

How is propionic acid $ C{H_3}C{H_2}COOH $ synthesized?

Answer 1

Hint: Propionic acid as suggested by its name and formula is an organic compound containing a three membered carbon chain where one of them is a functional group called the carboxylic acid group. The synthesis can be started with simple hydrocarbons followed by oxidation reactions.

Complete answer:
Propionic acid is the third member of the carboxylic acid series. Therefore the synthesis of this compound requires the involvement of reactants with three carbon atoms or a reaction that can allow stepping up the series. One such reaction involves the use of syngas and a two-membered unsaturated hydrocarbon.
Syngas contains a mixture of carbon monoxide and hydrogen gas which can be used for a variety of industrial processes. The reaction of ethene with syn gas results in the formation of a three-membered organic compound called the propionaldehyde. The reaction between syngas and ethene can be shown as follows:
 $ C{H_2} = C{H_2} + CO({H_2}) \to C{H_3}C{H_2}CHO $
The propionaldehyde contains a carbonyl group and three carbon atoms in its chain. A simple oxidation of aldehyde would result in the formation of a carboxylic acid group. Thus propionaldehyde can be transformed into propionic acid by using strong oxidizing agents like potassium permanganate. The reaction can be shown as follows:
 $ C{H_3}C{H_2}CHO\xrightarrow{{KMn{O_4}(oxidation)}}C{H_3}C{H_2}COOH $
 $ \Rightarrow $ Thus the two step synthesis of propionic acid involves the reaction of syngas with ethene followed by oxidation.

Note:
The syngas mixture can itself be obtained from hydrocarbons like methane that are abundantly available in nature. There can be more than one method of synthesis of the same organic compound as a variety of reagents can bring about the same transformations.