Test Index

NCERT Class XII Chemistry
Chapter - Alcohols, Phenols and Ethers
Questions with Solutions

© examsnet.com
Question : 25 of 45
Marks: +1, -0
Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.
Solution:  
The main limitation of Williamson’s ether synthesis lies in its unemployability for preparation of unsymmetrical ethers where the compound contains secondary or tertiary alkyl groups.
e.g., reaction between tert-butyl bromide and sodium methoxide yieldsan alkene
H3C−C∣CH3∣CH3−Brtret-Butylbromide+NaOCH3→H3C−C∥CH2∣CH32-Mthylpropane+NaBr+CH3OH\underset{\text{tret-Butylbromide}}{\mathrm{H_3C-}\underset{\mathrm{CH}_3}{\underset{\vert}{\overset{\mathrm{CH}_3}{\overset{\vert}{\mathrm{C}}}}}\mathrm{-Br}} + \mathrm{NaOCH_3} \rightarrow \underset{\text{2-Mthylpropane}}{\mathrm{H_3C-}\underset{\mathrm{CH}_3}{\underset{\vert}{\overset{\mathrm{CH}_2}{\overset{\parallel}{\mathrm{C}}}}}} + \mathrm{NaBr} + \mathrm{CH_3OH}
This is because the competing elimination reaction predominates over SN2\mathrm{S_N2} and alkene is formed.
© examsnet.com
Go to Question:
Prev Question
Next Question