JEE Chemistry 2025 Question with Solution

Given: Four carboxylic acid derivatives $p$, $q$, $r$ and $s$ are given.

Find: The correct order of rate of hydrolysis.

Hydrolysis of carboxylic acid derivatives proceeds through nucleophilic acyl substitution. The rate depends mainly on:

1. electrophilicity of the carbonyl carbon, and
2. stability of the leaving group.

The leaving groups are:

• for $p$: $\text{Cl}^-$
• for $q$: $\text{CH}_3\text{COO}^-$
• for $r$: $\text{CH}_3\text{CH}_2\text{O}^-$
• for $s$: $\text{NH}_2^-$

From the strength of their conjugate acids,

$$\text{HCl} > \text{CH}_3\text{COOH} > \text{CH}_3\text{CH}_2\text{OH} > \text{NH}_3$$

so the basicity order of the leaving groups is

$$\text{NH}_2^- > \text{CH}_3\text{CH}_2\text{O}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$$

Therefore, leaving group ability is

$$\text{Cl}^- > \text{CH}_3\text{COO}^- > \text{CH}_3\text{CH}_2\text{O}^- > \text{NH}_2^-$$

Hence the hydrolysis rate order is

$$(p) > (q) > (r) > (s)$$

This is also supported by electrophilicity: acyl chloride is most reactive, then anhydride, then ester, and amide is least reactive.

Therefore, the correct order of rate of hydrolysis is $p > q > r > s$. The correct option is D.

The solution marks option C, but its own working concludes $p > q > r > s$. Hence the worked solution supports D, not C.