NEET 2025 — Chemistry solution

NEET2025Chemistry

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): CH $_{3}$ CH $_{2}$ CH $_{2} -$ I undergoes S $_{N}$ 2 reaction faster than CH $_{3}$ CH $_{2}$ CH $_{2} -$ Cl.

Reason (R): Iodine is a better leaving group because of its large size.

In the light of the above statements, choose the correct answer from the options given below:

A
Both A and R are true and R is the correct explanation of A.
B
Both A and R are true but R is not the correct explanation of A.
C
A is true but R is false
D
A is false but R is true

Solution

Rate of S $_{N}$ 2 is proportional to the leaving ability of the group attached to the substrate carbon. Iodide (I $^{-}$ ) is a better leaving group than chloride (Cl $^{-}$ ) because of its larger size and lower charge density, which stabilises the leaving group after departure.

So both Assertion and Reason are true, and the Reason correctly explains the Assertion.

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