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MHT CET 202625 AprilEvening Shift
Exam
MHT CET
Year
2026
Date
25 April
Shift
Evening Shift
Subject
Chemistry
Chapter
Hydrocarbons

MHT CET 2026 · 25 April · Evening Shift · Chemistry · Hydrocarbons

H_3C-CH=CH_2 + H-Br (C_6H_5CO)_2O_2,\ Benzoyl peroxide...

H3C−CH=CH2+H−Br→(C6H5CO)2O2, Benzoyl peroxideH3C−CH2−CH2−Br\text{H}_3\text{C}-\text{CH}=\text{CH}_2 + \text{H}-\text{Br} \xrightarrow{\large{(\text{C}_6\text{H}_5\text{CO})_2\text{O}_2,\ \text{Benzoyl peroxide}}} \text{H}_3\text{C}-\text{CH}_2-\text{CH}_2-\text{Br}
Which of the following rules is followed when the above reaction occurs?

Options

  1. AMarkovnikovs rule
  2. BAnti-Markovnikovs rule
  3. CSaytzeff rule
  4. DHuckel rule

Correct answer

B. Anti-Markovnikovs rule

Step-by-step solution

The addition of HBr\text{HBr} to an unsymmetrical alkene in the presence of a peroxide (such as benzoyl peroxide) proceeds via a free radical mechanism.

The bromine free radical adds to the less substituted carbon atom of the double bond to generate a more stable secondary free radical intermediate.

This leads to the formation of 1-bromopropane (H3C−CH2−CH2−Br\text{H}_3\text{C}-\text{CH}_2-\text{CH}_2-\text{Br}) as the major product.

This regioselectivity is opposite to Markovnikov's rule and is known as the peroxide effect, Kharasch effect, or Anti-Markovnikov's rule.

Answer: Anti-Markovnikovs rule
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