Question

Assertion (A) $S _{ N } 1$ reaction is accompanied by racemisation.
Reason (R) Carbocation is formed in this reaction, and attack of nucleophile can be from either side of the leaving group.

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$
• C. $A$ is correct; $R$ is incorrect
• D. $R$ is correct; $A$ is incorrect

Answer 1

Answer: (A)

In case of optically active alkyl halides, $S _{ N }$ 1 reactions are accompanied by racemisation. The carbocation formed in the slow step being $s p^{2}$ hybridised is planar (achiral). The attack of the nucleophile may be from either side resulting mixture of products. One product has same configuration, while other has opposite configuration.