Q18 / 150 · MHT CET 2026 (19 April Shift 2) · Chemistry
Identify the major product of following reaction.
$\text{Propene} \xrightarrow[\large{\text{Peroxide}}]{\large{\text{HBr}}} \,?$
$\text{Propene} \xrightarrow[\large{\text{Peroxide}}]{\large{\text{HBr}}} \,?$
- Correct answerA1 - Bromopropane
- B2 - Bromopropane
- C3 - Bromopropene
- D2 - Bromopropan-1-ol
Solution
The reaction of propene with $HBr$ in the presence of peroxide proceeds via a free radical mechanism, known as the peroxide effect or anti-Markovnikov addition.
The peroxide undergoes homolytic cleavage to form alkoxy radicals, which then abstract a hydrogen atom from $HBr$ to generate a bromine radical ($Br^{\bullet}$).
The bromine radical adds to the less substituted carbon atom of the double bond in propene to generate a more stable secondary free radical:
$CH_3-CH=CH_2 + Br^{\bullet} \rightarrow CH_3-\dot{C}H-CH_2Br$
The secondary free radical then abstracts a hydrogen atom from another molecule of $HBr$ to form the final product:
$CH_3-\dot{C}H-CH_2Br + HBr \rightarrow CH_3-CH_2-CH_2Br + Br^{\bullet}$
The major product formed is 1-bromopropane.
Answer: 1 - Bromopropane
The peroxide undergoes homolytic cleavage to form alkoxy radicals, which then abstract a hydrogen atom from $HBr$ to generate a bromine radical ($Br^{\bullet}$).
The bromine radical adds to the less substituted carbon atom of the double bond in propene to generate a more stable secondary free radical:
$CH_3-CH=CH_2 + Br^{\bullet} \rightarrow CH_3-\dot{C}H-CH_2Br$
The secondary free radical then abstracts a hydrogen atom from another molecule of $HBr$ to form the final product:
$CH_3-\dot{C}H-CH_2Br + HBr \rightarrow CH_3-CH_2-CH_2Br + Br^{\bullet}$
The major product formed is 1-bromopropane.
Answer: 1 - Bromopropane
Hence, the correct answer is option: 'A'.