Question

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Hydrolysis of an alkyl chloride is a slow reaction but in the presence of NaI, the rate of the hydrolysis increases
Reason R: $\,I ^{-}$is a good nucleophile as well as a good leaving group
In the light of the above statements, choose the correct answer from the options given below

• A. A is false but $R$ is true
• B. A is true but $R$ is false
• C. Both $A$ and $R$ are true but $R$ is $N O T$ the correct explanation of $A$
• D. Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

Answer 1

The Correct Option is D

1. Assertion (A): - Hydrolysis of alkyl chlorides is typically a slow reaction because the leaving group (\(\text{Cl}^-\)) is not very efficient. 
- However, in the presence of \(\text{NaI}\), \(\text{I}^-\) displaces \(\text{Cl}^-\) in an \(S_N2\) substitution reaction, forming alkyl iodides. - Alkyl iodides hydrolyze faster due to the better leaving group (\(\text{I}^-\)). 
- Therefore, Assertion (A) is true. 

2. Reason (R): - \(\text{I}^-\) is both a good nucleophile and an excellent leaving group. This property enhances the \(S_N2\) reaction rate and increases the hydrolysis rate.
- Hence, Reason (R) is true. 

3. Relationship between A and R: - The presence of \(\text{NaI}\) enhances the hydrolysis rate primarily because \(\text{I}^-\) is a better nucleophile and a better leaving group than \(\text{Cl}^-\). - This is consistent with the assertion and explains the observed phenomenon. 
- Thus, Reason (R) correctly explains Assertion (A).