Question

The rate of $S_{N}2$ reaction is maximum when the solvent is:

• A. $C{H}_{3}OH$
• B. $H_{2}O$
• C. DMSO
• D. Benzene

Answer 1

Answer: (C)

DMSO

The rate of $S{N}^2$ reaction is maximum when the solvent is polar aprotic such as DMSO (dimethyl sulphoxide) $(C{H}_3{)}_{2}S\to O$. In such solvents, the nucleophile is not solvated and can freely attack the substrate. Also, the polar nature of the solvent helps in the cleavage of $C-X$ bond where X is the leaving group.