Question

The total number among following ethers which cannot be prepared by Williamson's synthesis is:
$CH_3OCH_2CH_3, C_6H_5OCH_3, (C_6H_5)_2O, (CH_3)_3COCH_3, (C_2H_5)_2O, (CH_3)_3C - O - C(CH_3)_3$

Answer 1

In Williamson's synthesis,
i. $1^\circ $ alkyl halide and $3^\circ $ alkoxide give the best yield of corresponding ethers.
ii. In case of, $3^\circ $ alkyl halide, elimination competes over substitution and alkene is obtained as a product.
iii. Aryl halides do not undergo nucleophilic substitution unless it is activated by the presence of electron-withdrawing group.
Thus, $\left(C_{6} H_{5}\right)_{2}O$ and $\left(CH_{3}\right)_{3}C-O-C\left(CH_{3}\right)_{3}$ cannot be prepared by Williamson's synthesis.