Question

What is the correct method to synthesize 2-ethoxy-2-methylpropane, \( (CH_3)_3C-O-C_2H_5 \), by Williamson's synthesis?

• A. Using t-butyl alkoxide and ethyl chloride
• B. Using t-butyl chloride and ethoxide
• C. Using t-butanol and ethanol
• D. Using isopropyl chloride and isopropoxide

Hint:

Think about which alkyl halide can undergo a clean SN2 reaction without competing elimination.

Answer 1

The Correct Option is A

Step 1: The target molecule 2-ethoxy-2-methylpropane is the ether \( (CH_3)_3C-O-C_2H_5 \), built from a tertiary tert-butyl fragment and an ethyl fragment joined through an oxygen atom.

Step 2: Williamson ether synthesis is an \( S_N2 \) reaction in which an alkoxide ion displaces a halide ion from an alkyl halide. The reaction works best when the carbon bearing the leaving group is primary, since a bulky nucleophile cannot easily approach a crowded tertiary carbon.

Step 3: If tert-butyl chloride is combined with ethoxide ion, the ethoxide would have to attack a tertiary carbon. This is sterically blocked for \( S_N2 \), so the strong, small base instead pulls off a proton and gives elimination (E2), forming isobutylene rather than the ether.

Step 4: If tert-butyl alkoxide is combined with ethyl chloride instead, the bulky tert-butoxide only needs to act as a nucleophile toward the unhindered primary carbon of ethyl chloride. This \( S_N2 \) substitution proceeds cleanly and gives the required ether.

Step 5: Therefore the correct route uses t-butyl alkoxide with ethyl chloride.

\[ \boxed{\text{t-butyl alkoxide + ethyl chloride}} \]