Q. Propylene on treatment with $H B r / H_{2} O_{2}$ provides

2115 220 KEAMKEAM 2019Hydrocarbons Report Error

A

1 -bromopropane

53%

B

2-bromopropane

12%

C

1,2-bromopropane

19%

D

1-bromopropane-2-ol

6%

E

2-bromopropane-1-ol

6%

Solution:

Addition of HBr to unsymmetrical alkenes takes place contrary to the markovnikov's rule in presence of peroxide.

Propylene on treatment with $H B r / H_{2} O_{2}$ provides l-bromopropane. In the presence of peroxide $(H_{2} O_{2})$ , addition of $H B r$ to unsymmetrical alkenes like propylene takes place contrary to the Markovnikov's rule. This happens only with $H B r$ but not with HCl and HI.

Reaction of propylene with $H B r / H_{2} O_{2}$ is as follows

$P ro p y l e n e C H_{3} C H = C H_{2} + H B r H_{2} O_{2} 1 B ro m o p ro p an e C H_{3} - C H_{2} C H_{2} B r$