Which of the following statements best describes the Williamson ether synthesis for preparing unsymmetrical ethers?

• A. It uses the reaction of two alkyl halides in the presence of a base to form an ether.
• B. It is the acid-catalyzed dehydration of two alcohol molecules to form an ether.
• C. It is the addition of water to an alkene to produce an ether.
• D. It involves the reaction of an ${\mathrm{alkoxide}}_{\mathrm{ion}}$ with a ${\mathrm{primary}}^{\mathrm{alkylhinspace\; halide}}$ to form an ether.

Answer: (D)

Verified step by step guidance

1. Understand that the Williamson ether synthesis is a method to prepare ethers, especially unsymmetrical ethers, by reacting an alkoxide ion with an alkyl halide.
2. Recognize that the alkoxide ion (RO\textsuperscript{-}) acts as a nucleophile, which means it donates an electron pair to form a new bond.
3. Identify that the alkyl halide involved is typically a primary alkyl halide, which is more susceptible to nucleophilic substitution reactions (SN2 mechanism).
4. The reaction proceeds via an SN2 mechanism where the alkoxide ion attacks the electrophilic carbon attached to the halide, displacing the halide ion and forming the ether bond.
5. Summarize that the Williamson ether synthesis is not a reaction between two alkyl halides, nor an acid-catalyzed dehydration of alcohols, nor an addition of water to alkenes, but specifically the nucleophilic substitution of an alkyl halide by an alkoxide ion.