Question

Please give clean and percise responses. Thank you.

A.In principle , radicals could add to styrene at the carbon atom bearing the phenyl group rather the other one, yet they do not. Explain the basis of this selectivity for the addition reaction?

B. Why is tert-butyl peroxybenzoate a good radical initiator?

Answer 1

Answer-A) In Styrene firstly an initiator molecule adds at terminal C and gives the radical formation at benzylic position (The C which bears phenyl group). The benzylic radical is well stabilized through resonance in phenyl ring. As the radical formed at benzylic position is stable it exist for sufficiently more time so that other radical forms bond with it. And hence radical could add the styrene molecule at C bearing phenyl group. We can see diagram showing the resonance stability at benzylic position.

Answer-B) tert- Butyl peroxybenzoate in presence of light energy will dissociates in 2 possible ways as we can see in diagram. In either way the radicals generated gain stability e.g. tert-Butyl group through hyperconjuagation. As t-Butyl peroxybenzoate gives stable radicals it is a good radical initiator.