question_answer 37)

Illustrate the examples the limitations of Williamson'ssynthesis for the preparation of certain types of ethers. Tertiary alkyl halides readily give elimination product with strong baseslike alkoxide ions. The C—X bond of alkyl halide does not possess doublebond character i.e., should not be in conjugation with multiple bond.  

Answer:

(i) In Williamson's synthesis reaction for the preparation orether, the alkyl halide used must be primary as tertiary halidesreadily undergo elimination with strong bases like . Thisis be best understood by taking the example of preparation ofethyl tertiary butyl ether. For which the reactants used are ethylbromide and sodium tertiary butoxide, but not the tertiary butylchloride and sodium ethoxide.   (ii) Aryl halides and vinyl halides cannot be used as substrates because they are less reactive in nucleophilic substitution.