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Question: Which of the following compound is most rapidly hydrolyzed by SN2 mechanism?...

Which of the following compound is most rapidly hydrolyzed by SN2 mechanism?

A

(CH3)2CHBr

B

CH3CH2Br

C

(CH3)3CBr

D

(CH3CH2)3CBr

Answer

CH3CH2Br

Explanation

Solution

The SN2 mechanism is a concerted reaction where the nucleophile attacks the carbon bearing the leaving group from the backside. The rate of an SN2 reaction is highly sensitive to steric hindrance around the carbon atom undergoing substitution. Less steric hindrance leads to a faster reaction.

The general order of reactivity for SN2 reactions is:

Methyl halides > Primary (1°) alkyl halides > Secondary (2°) alkyl halides >> Tertiary (3°) alkyl halides. Tertiary halides are generally unreactive towards SN2 reactions due to high steric hindrance.

Comparing the types of alkyl halides, primary alkyl halides offer the least steric hindrance at the reaction center, making them the most reactive towards SN2 hydrolysis. Therefore, CH3CH2Br will undergo hydrolysis most rapidly by the SN2 mechanism.