Question

Williamson’s synthesis of preparing dimethyl ether is a/an:

• A. Electrophilic substitution
• B. \( S_N1 \) reaction
• C. Electrophilic addition
• D. \( S_N2 \) reaction

Hint:

Williamson synthesis requires primary alkyl halides to avoid elimination. Use \( S_N2 \) route with strong nucleophile like alkoxide.

Answer 1

The Correct Option is D

Williamson's synthesis is used to prepare ethers by reacting an alkoxide ion with a primary alkyl halide.
Example: \[ \text{CH}_3\text{ONa} + \text{CH}_3\text{Br} \rightarrow \text{CH}_3\text{OCH}_3 + \text{NaBr} \] - Here, the nucleophile \( \text{CH}_3\text{O}^- \) attacks the carbon of the alkyl halide in a one-step mechanism. - The reaction proceeds via a backside attack — a hallmark of \( S_N2 \) (bimolecular nucleophilic substitution). - No carbocation is formed, which eliminates the possibility of an \( S_N1 \) mechanism. \[ \boxed{\text{Williamson synthesis proceeds via } S_N2 \text{ mechanism.}} \]