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Styrene (Ph-CH=CH2) reacts with BrCCl3 in the presence of a peroxide initiator. What is the major product?

1. Ph-CH(Br)-CH2-CCl3
2. Ph-CH(CCl3)-CH2-Br
3. Ph-C(Br)=CH-CCl3
4. Ph-CH2-CH(Br)-CCl3

Correct answer: Ph-CH(Br)-CH2-CCl3

Solution

Peroxide-initiated radical chain: CCl3 radical (from BrCCl3) adds to the terminal CH2 of styrene, forming a stable benzylic radical at the Ph-CH position, which then abstracts Br from another BrCCl3, giving Ph-CH(Br)-CH2-CCl3.

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