Question

Reaction of HBr with propene in the presence of peroxide gives

• A. isopropylbromide
• B. 3-bromopropane
• C. allylbromide
• D. n-propylbromide

Answer 1

The correct option is D n-propylbromide

According to Markovnikov's rule, negative part of addendum (adding molecule) gets attached to that doubly bonded C which posses lower number of hydrogen atoms. In presence of peroxide, HBr adds on alkenes in anti-markovnikov's way, thus
$\underset{\text{Propene}}{H_{3}C-CH=C{H}_2}+HBr\stackrel{\text{Peroxide}}{\to }\underset{n-propylbromide}{H_{3}C-C{H}_2-C{H}_{2}Br}$
Kharasch observed that the addition of HBr to unsymmetrical alkene in the presence of organic peroxide follows an opposite course to that suggested by Markovnikov. This is termed anti-Markovnikov or peroxide effect.