Question

3-Methylhex-2-ene on reaction with HBr in presence of peroxide forms an addition product (A). The number of possible stereoisomers for 'A' is ______.

Answer 1

Correct Answer: 4

To solve this problem, we need to analyze the reaction of 3-Methylhex-2-ene with HBr in the presence of peroxide. This is a classic example of anti-Markovnikov addition due to the peroxide effect, resulting in the following steps:

1. Initial Reaction: In the presence of peroxide, HBr adds to the alkene via a radical mechanism. The addition occurs at the terminal carbon to form the anti-Markovnikov product.
2. Structural Analysis: The product of this reaction is 1-bromo-3-methylhexane.
3. Chirality Considerations: In 1-bromo-3-methylhexane, two chiral centers are present at C-2 and C-3.
4. Stereoisomers Calculation: The number of possible stereoisomers is given by 2ⁿ, where n is the number of chiral centers. Here, n = 2, thus 2² = 4 stereoisomers are possible.
5. Verification: These stereoisomers correspond to different spatial arrangements at C-2 and C-3: RR, SS, RS, and SR configurations.
6. Range Validation: The computed solution, 4, falls within the given range (4,4).

Thus, the number of possible stereoisomers for the addition product 'A' is 4.

Answer 2

The structure of the product formed will have two chiral centers due to anti-Markovnikov addition of HBr in the presence of peroxide:
With two chiral centers, the number of stereoisomers is:

\[ 2^{\text{chiral centers}} = 2^2 = 4 \]