Question

What is the major product formed when Propene reacts with \(HBr\) in the presence of peroxide?

• A. \(2\)-Bromopropane
• B. \(1\)-Bromopropane
• C. \(1,2\)-Dibromopropane
• D. Propane

Hint:

Remember: \(HBr\) in the presence of peroxide follows the Anti-Markovnikov rule (Peroxide Effect). This effect is observed only with \(HBr\), not with \(HCl\) or \(HI\).

Answer 1

The Correct Option is B

Concept: In the presence of peroxide, the addition of \(HBr\) to an alkene follows the Anti-Markovnikov rule. According to this rule:
• The bromine atom attaches to the carbon having more hydrogen atoms.
• The hydrogen atom attaches to the more substituted carbon. This reaction proceeds through a free radical mechanism and is commonly known as the Peroxide Effect or Kharasch Effect.

Step 1: Identify the structure of Propene. \[ CH_3 - CH = CH_2 \]

Step 2: Apply the Anti-Markovnikov rule. The bromine atom attaches to the terminal carbon (which has more hydrogen atoms), leading to the formation of: \[ CH_3 - CH_2 - CH_2Br \]

Step 3: Identify the product formed. \[ \text{Product: } 1\text{-Bromopropane} \]