Williamson ether synthesis uses what reagents?

• A. A Grignard reagent and water.
• B. An alkoxide and a primary alkyl halide.
• C. A sulfonate and a base.
• D. A dehydrating agent and alcohol.

Answer: (B)

The key idea is forming an ether via an SN2 substitution where an alkoxide acts as the nucleophile and a primary alkyl halide serves as the electrophile. In the Williamson ether synthesis, you generate a strong alkoxide by deprotonating an alcohol with a base, and then that alkoxide attacks a primary alkyl halide, displacing the halide to give the ether R–O–R'. The primary substrate is important because SN2 works best without competition from elimination on more substituted carbons.

Why this pairing is the best fit: an alkoxide is the reactive nucleophile needed to form the C–O bond in a single concerted step, and a primary alkyl halide provides a good leaving group-bearing carbon for SN2 attack. The other options fail to provide this SN2-bearing combination: a Grignard reagent would be quenched by water and not form an ether; a sulfonate with a base doesn’t supply the necessary nucleophile to attack a leaving group in this context; and a dehydrating agent with an alcohol forms ethers by acid-catalyzed dehydration, a different mechanism than the Williamson approach.