Which of the following cannot be made by using Williamson's synthesis?

CONCEPT:

Williamson's Synthesis

• Williamson's synthesis is a method used to prepare ethers by reacting an alkoxide ion with a primary alkyl halide.
• The general reaction is:

  R-O^- + R'-X → R-O-R' + X^-

• This method is not suitable for preparing ethers with tertiary alkyl halides because tertiary alkyl halides undergo elimination reactions (E2) rather than substitution reactions (S_N2).

EXPLANATION:

• In the given options:
  • 1) Methoxybenzene: Can be prepared using Williamson's synthesis.
  • 2) Benzyl p-nitrophenyl ether: Can be prepared using Williamson's synthesis.
  • 3) Methyl tertiary butyl ether: Can be prepared using Williamson's synthesis.
  • 4) Di-tert-butyl ether: Cannot be prepared using Williamson's synthesis because it involves tertiary alkyl halides which favor elimination.

Therefore, the correct answer is option 4: Di-tert-butyl ether cannot be made by using Williamson's synthesis.