Question:

In Williamson synthesis of mixed ether having a primary and a tertiary alkyl group if tertiary halide is used, then :

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Williamson synthesis is \(\mathrm{S_N2}\); an alkoxide is also a strong base.
Updated On: Oct 31, 2026
  • Rate of reaction will be slow due to slow cleavage of carbon-halogen bond.
  • Alkene will be the main product.
  • Simple ether will form instead of mixed ether.
  • Expected mixed ether will be formed.
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The Correct Option is B

Solution and Explanation

Williamson synthesis: \(\mathrm{R{-}ONa + R'{-}X \rightarrow R{-}O{-}R' + NaX}\), an \(\mathrm{S_N2}\) reaction.
With a tertiary alkyl halide, backside attack is blocked by steric hindrance, while the alkoxide ion acts as a strong base.
So the alkoxide abstracts a \(\beta\)-hydrogen (E2 elimination), giving an alkene, e.g. \(\mathrm{(CH_3)_3C{-}Br + C_2H_5O^- \rightarrow (CH_3)_2C{=}CH_2}\).
Hence the alkene is the main product, not the ether.
Answer: (2) Alkene will be the main product.
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