When 3-phenyl propene reacts with HBr in presence of peroxide the product obtained is :

Question

Accepted Answer

When 3-phenyl propene reacts with HBr in the presence of peroxide, the reaction follows the anti-Markovnikov rule due to the peroxide effect (also known as the Kharasch effect). This rule states that in the presence of peroxides, the addition of HBr to alkenes occurs such that the bromine atom attaches to the less substituted carbon atom of the double bond.

1. **Explanation for Option 1 (1-Bromo-3-phenyl propane):**
   - In the case of 3-phenyl propene, the double bond is between the first and second carbon atoms of the propene chain. According to the anti-Markovnikov rule, the bromine atom will attach to the less substituted carbon, which is the first carbon in this case. This results in the formation of 1-bromo-3-phenyl propane. Therefore, Option 1 is correct.

2. **Explanation for why other options are incorrect:**
   - **Option 2 (2-Bromo-3-phenyl propane):** This product would result from a Markovnikov addition, where the bromine atom attaches to the more substituted carbon atom. However, in the presence of peroxides, the reaction follows the anti-Markovnikov rule, making this option incorrect.
   - **Option 3 (1,2-Dibromo-3-phenyl propane):** This product suggests the addition of two bromine atoms across the double bond, which is not the case in this reaction. The presence of peroxides leads to the addition of only one bromine atom, not two, making this option incorrect.
   - **Option 4 (1,1-Dibromo-3-phenyl propane):** Similar to Option 3, this option implies the addition of two bromine atoms, which does not occur in this reaction. The peroxide effect results in the addition of a single bromine atom to the less substituted carbon, making this option incorrect.

In conclusion, the reaction of 3-phenyl propene with HBr in the presence of peroxide follows the anti-Markovnikov rule, leading to the formation of 1-bromo-3-phenyl propane, which is why Option 1 is the correct answer.