Previous Year NEET Question- Haloalkanes L-4

Question: Which of the following undergoes nucleophilic substitution exclusively by $\mathrm{S}_{\mathrm{N}} 1$ mechanism?#

A) Ethyl chloride

B) Isopropyl chloride

C) Chlorobenzene

D) Benzyl chloride

Answer: Benzyl chloride#

Sol:#

$\mathrm{S}_{\mathrm{N}} 1$ reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens and nature of carbonium ion in substrate is

Benzyl $>$ Allyl $>$ Tertiary $>$ Secondary $>$ Primary $>$ Methyl halides.