Which of the following compound cannot be prepared by Williamson's synthesis?

Step-by-step solution

Williamson synthesis involves the reaction of an alkoxide ion with an alkyl halide via an S_ N 2 mechanism. Since S_ N 2 reactions are highly sensitive to steric hindrance, the alkyl halide used must be primary for the reaction to proceed efficiently. If a tertiary alkyl halide is used, elimination (E2) becomes the dominant pathway, leading to the formation of an alkene instead of an ether. In the case of ( CH ₃ )₃ COC ( CH ₃ )₃ (di-tert-butyl ether), the synthesis would require the reaction of a tert-butoxide ion