Question

The –COOH group in the carboxylic acid can be replaced by H by heating the acid with:
A. Zn with HCl
B. $H_2$ in presence of nickel
C. Soda lime
D. Bromine and concentrated aqueous alkali.

Answer 1

Hint: The decarboxylation reaction is defined as the reaction, where the carboxyl group is removed with the release of carbon dioxide and hydrogen atom is added. In this reaction the unsaturated compound gives a saturated product.

Complete step by step answer:
The carboxylic acid group cannot be reduced by zinc amalgam in presence of hydrochloric acid. The zinc amalgam in presence of hydrochloric acid is used to reduce carbonyl compounds ketone and aldehyde and the reaction is known as Clemmensen reduction.
The catalytic hydrogenation of the carboxylic group converts it to alcohol. Therefore, the –COOH group in the carboxylic acid cannot be replaced by H by heating the acid with $H_2$ in presence of nickel.
The sodium salt of carboxylic acid reacting with soda lime undergoes a decarboxylation reaction to form methane and sodium carbonate. Thus, the –COOH group in the carboxylic acid can be replaced by H by heating the acid with soda lime.
The reaction is shown below.
$C{H}_{3}COONa+NaOH\to C{H}_4+N{a}_{2}C{O}_3$
The carboxylic acid on reaction with Bromine and concentrated aqueous alkali give alpha-bromination of carboxylic acid.
Thus, the –COOH group in the carboxylic acid can be replaced by H by heating the acid with soda lime.

So, the correct answer is Option C.

Note: In the given reaction between the sodium salt of carboxylic acid and soda lime, the soda lime is shown by the formula of solid sodium hydroxide. The soda lime is the mixture of sodium hydroxide and calcium hydroxide.