JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Alcohols Phenols and Ethers

A Williamson synthesis gives a good yield of ether only when the alkyl halide is methyl or primary, so that substitution outruns elimination, while the alkoxide may be bulky. The reactions of tert-butoxide with ethyl bromide, of cyclohexanolate with methyl bromide, and of phenolate with n-propyl bromide all use unhindered methyl or primary halides and deliver the ether cleanly. Using a secondary halide such as sec-butyl bromide with isobutoxide instead lets the strongly basic alkoxide remove a beta-hydrogen, so elimination dominates and little ether forms. The combination of isobutoxide with sec-butyl bromide fails to give the ether in major proportion.