JEE Main · 2023 · 10 Apr 2023 · Shift 1 · Alcohols Phenols and Ethers

Methyl phenyl ether, anisole, is made by the Williamson synthesis, in which an alkoxide or phenoxide ion displaces halide from an alkyl halide in an $S_{N}2$ step. The fragments must be chosen so that the carbon attacked belongs to an alkyl halide, not an aryl halide, since an aryl halide will not undergo $S_{N}2$. Taking sodium phenoxide as the nucleophile and methyl bromide as the substrate, the phenoxide oxygen attacks the methyl carbon and expels bromide to give ${\text{Ph-O-CH}}_3$. Pairing an aryl halide with methoxide fails because the aromatic C-Br bond is inert to this substitution, and phenoxide with methanol offers no alkylating agent. The suitable conditions are sodium phenoxide with methyl bromide.