Question

Assertion (A): $C{{H}_{3}}CN$ on hydrolysis gives Acetic acid.
Reason (R): Cyanides on hydrolysis liberates $N{{H}_{3}}$ gas.
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true and R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.

Answer 1

Hint: To find out the correct option for this type of question, first try to state the process of cyanide hydrolysis and what are the products formed in the reaction and mention the reason for the formation of the product. Then, try to select the suitable option.

Complete step by step answer:
Here, given that $C{{H}_{3}}CN$on hydrolysis gives acetic acid and the reason states that cyanides on hydrolysis liberates $N{{H}_{3}}$ gas.
So, to find the correct explanation, we have to look at the hydrolysis of the cyanides. And we know that cyanide is a nitrile. So, straightforwardly, we have to look at the process of hydrolysis of the nitrile compounds.
Nitriles are the organic compounds in the organic chemistry which are also called as cyano compounds, as it has the functional group called cyano group which is represented by $-C\equiv N$, and it is attached to a substituent carbon body i.e. $R-C\equiv N$.
Nitrile undergoes various processes of reactions, from which hydrolysis stands one.
So, in hydrolysis of nitriles with water and in presence of an acid, the product will be formed will be a carboxylic acid eliminating ammonia gas, $N{{H}_{3}}$. The reaction is shown as:
$RCN\xrightarrow{{{H}_{2}}O}RCOOH+N{{H}_{3}}$

Thus, it is proved that cyanides on hydrolysis will liberate $N{{H}_{3}}$ gas. So, the reason is correct.
Now, considering the side chain i.e. the R-group to be a methyl group in the nitrile, on its hydrolysis, the reaction will be:
$C{{H}_{3}}CN\xrightarrow{{{H}_{2}}O}C{{H}_{3}}COOH+N{{H}_{3}}$

So, we can see that the product formed on hydrolysis of $C{{H}_{3}}CN$ are acetic acid ($C{{H}_{3}}COOH$) and ammonia gas ($N{{H}_{3}}$). So, the assertion given is correct and the reason explains the assertion.
So, the correct answer is “Option A”.

Note: Nitriles are reduced to primary and tertiary amines by treating them with lithium aluminium hydride. The reduction process occurs in the presence of some catalysts. While the alkylation of nitrile compounds leads to the formation of nitrile anions and the hydrolysis of nitriles in the presence of an acid or a base will produce carboxamides and carboxylic acids.