question_answer 128)

  Some alkyl halides undergo substitution whereas some undergo elimination reaction on treatment with bases. Discuss the structural features of alkyl halides with the help of examples which are responsible for this difference.

Answer:

  Primary and secondary alkyl halides prefer to undergo substitution reactions by  mechanism while tert- n-butyl halides prefer to undergo elimination reactions due to the formation of stable carbocations. For example, butyl bromide and sec-butyl bromide on treatment with aqueous KOH undergo substitution reactions to afford the corresponding alcohols, i.e., n-butyl alcohol and -butyl alcohol respectively. In contrast tert-buty bromide on treatment with aqueous KOH preferentially undergoes elimination to form isobutylene as the major product. Write equations yourself.