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

To determine the correct relationship between Assertion A and Reason R, we need to analyze both statements individually and then determine their connection.

1. Assertion A: Hydrolysis of an alkyl chloride is a slow reaction but in the presence of NaI, the rate of the hydrolysis increases.
   • Alkyl chlorides (R-Cl) can undergo hydrolysis to form alcohols. However, this reaction is generally slow because the chloride ion (\(Cl^{-}\)) is not an efficient leaving group.
   • When an alkyl chloride is treated with sodium iodide (NaI), the iodide ion (\(I^{-}\)) replaces the chloride ion due to its stronger nucleophilicity. Furthermore, iodide is a better leaving group than chloride.
   • As a result, the overall process occurs faster because \(I^{-}\) is both a good nucleophile and a good leaving group compared to \(Cl^{-}\).
2. Reason R: \(I^{-}\) is a good nucleophile as well as a good leaving group.
   • This statement correctly describes the characteristics of the iodide ion. \(I^{-}\) is larger than most other halide ions, allowing it to polarize easily, which enhances its nucleophilicity and ability to leave during substitution reactions.
3. Linking the Assertion and Reason:
   • Both Assertion A and Reason R are true statements. Reason R provides the exact explanation for Assertion A.
   • The presence of a better nucleophile and better leaving group in the form of \(I^{-}\) accelerates the hydrolysis reaction of alkyl chlorides. Therefore, the increased reaction rate upon adding NaI is directly due to the properties of the iodide ion as stated in Reason R.

Hence, the correct answer is: Both A and R are true and R is the correct explanation of A.