MolSynapsequestion bank
MolSynapse / Question bank / Haloalkanes and Haloarenes / Preparation of alkyl and aryl halides
JEE Main levelSingle correct optionDifficulty 2 of 3hx115

Cyclohexene is treated with N-bromosuccinimide (NBS) in in the presence of light with a trace of peroxide. The main product is

  1. Abromocyclohexane
  2. B3-bromocyclohexene
  3. Ctrans-1,2-dibromocyclohexane
  4. D4-bromocyclohexene

Answer: B

NBS supplies a low steady concentration of , so allylic substitution by a radical chain beats addition to the double bond. The radical forms at the allylic carbon (resonance stabilised), giving 3-bromocyclohexene. Addition products need a high concentration.
Practice Haloalkanes and Haloarenes More on Preparation of alkyl and aryl halides
Previous questionNext question

More questions on Preparation of alkyl and aryl halides