The WILLIAMSON ETHER SYNTHESIS prepares ethers by reacting

1. NCERT §7.8 (Preparation of Ethers): the Williamson synthesis is the standard preparative route for unsymmetric ethers. 2. Generic reaction: $\mathrm{R{-}O^-Na^+} + \mathrm{R'{-}X} \to \mathrm{R{-}O{-}R'} + \mathrm{NaX}$. 3. The alkoxide (a strong nucleophile) attacks the alkyl halide via SN2 — back-side displacement of the leaving halide. 4. For best yield, use METHYL or PRIMARY alkyl halides (better SN2 substrates). Secondary alkyl halides give mixtures of substitution and elimination; tertiary halides give mostly elimination. 5. Example: $\mathrm{CH_3O^-Na^+ + CH_3CH_2Br \to CH_3{-}O{-}CH_2CH_3 + NaBr}$. 6. Option B is INTRAMOLECULAR/INTERMOLECULAR dehydration (gives symmetric ethers only, lower yield). Options C and D are unrelated. _Source: NCERT Class 12 Chemistry Part 2, Ch 7, §7.8 (Williamson ether synthesis), p. 21._