question_answer

Reaction of HBr with propene in the presence of peroxide gives:                          [AIPMT (S) 2004]

A) isopropyl bromide

B) 3-bromo propane

C) allyl bromide

D) n-propyl bromide

Correct Answer: D

Solution :

              

[d] Reaction of HBr with propene in the presence of peroxide gives n-propyl bromide. This addition reaction is an example of Anti-Markownikoff addition reaction.

(i.e., it is completed in form of free radical addition)

-propyl bromide

Mechanism of this reaction is represented as follows:

Step 1. Formation of free radical of peroxide by means of decomposition.

Step 2. Benzoate free radical forms bromine

free radical with HBr.

Step 3. Bromine free radical attacks on

of propene to form intermediate free radical.

Hence, is the major product of this step.

Step 4. More stable free radical accept hydrogen free radical from benzoic acid and give final product of reaction.

Step 5. Benzoate free radicals are changed into benzoyl peroxide for the termination of free radical chain.