Question: On acid hydrolysis, propane nitrile gives: A.) Propanal B.) Acetic acid C.) Propionamide D.)...

Question

On acid hydrolysis, propane nitrile gives:
A.) Propanal
B.) Acetic acid
C.) Propionamide
D.) Propanoic acid

Answer 1

Solution

To solve this question we need to know that when we do acid hydrolysis of any nitrile compound then corresponding carboxylic acid is obtained. We just need to replace $CN$ of the nitrile compound with $COOH$ group.

Complete step by step answer:
In this question, nitrile compound is a compound which contains $CN$ group. By acid hydrolysis we mean that reaction in which a proton $({H^ + })$ donating compound is used to catalyse the reaction. We can take an example of ${H_3}{O^ + }$ . In this reaction one part of the compound receives a proton $({H^ + })$ and the other part receives $(O{H^ - })$ from water.
When nitriles are acid hydrolysed they do so in two stages. In the first stage it forms the corresponding amide group and in second stage it forms corresponding carboxylic acid from the amide.
Step $1$ .) When propane nitrile will react with ${H_3}{O^ + }$ then it undergoes acid hydrolysis. In the first step, the $C \equiv N:$ will react with ${H_3}{O^ + }$ and then it will form a primary amide that is propanamide in this case. The reaction can be shown as:
$C{H_2} - C{H_2} - C \equiv N:\xrightarrow{{{H_{^3}}{O^ + }}}\left[ {C{H_2} - C{H_2} - CO - N{H_2}} \right]$
Step $2$ .) In second step, when the produced propanamide reacts again with ${H_3}{O^ + }$ then the $- N{H_2}$ will replace with $- OH$ group and the ${H^ + }$ ion will combine with $N{H_2}$ to form ammonia ( $N{H_3}$ ). This reaction can be shown as:
$C{H_2} - C{H_2} - CO - N{H_2}\xrightarrow{{{H_3}{O^ + }}}C{H_2} - C{H_2} - COOH + N{H_3}$
Hence, we can see that from acid hydrolysis of propane nitrile, propanoic acid is obtained as the end product and ammonia as by product.
Hence option (D) is correct.

Note:
In such questions, about acid hydrolysis of nitriles we should know that the reaction of nitrile with water in practical is a very slow reaction that it could be completely negligible. So, the nitrile is heated with dilute acids.