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 address this issue, the reaction of 3-Methylhex-2-ene with HBr under peroxide conditions requires analysis. This reaction exemplifies anti-Markovnikov addition via a radical pathway, proceeding as follows:

1. Reaction Initiation: Peroxides facilitate the addition of HBr to the alkene through a radical mechanism. Addition occurs at the terminal carbon, yielding the anti-Markovnikov product.
2. Product Identification: The resulting product is 1-bromo-3-methylhexane.
3. Chiral Center Identification: The molecule 1-bromo-3-methylhexane contains two chiral centers located at carbon atoms 2 and 3.
4. Stereoisomer Enumeration: The total number of stereoisomers is calculated using the formula 2ⁿ, where 'n' represents the number of chiral centers. With n = 2, the number of possible stereoisomers is 2² = 4.
5. Stereoisomer Confirmation: These stereoisomers represent distinct spatial configurations at C-2 and C-3, namely RR, SS, RS, and SR.
6. Range Check: The calculated result of 4 is consistent with the specified range (4,4).

Therefore, the number of stereoisomers for product 'A' is determined to be 4.