Question

What products would you expect from reaction of the following alkenes with NBS? If more than one product is formed, show the structures of all.

Short answer

In this reaction, the two product formed are not in equal proportions. The reaction at the two ends is not equal because of the formation of a unsymmetrical aromatic radical. Thus, the reaction at the primary end (which is less hindered) is favoured.

Step-by-step solution

Bromination of Cyclic alkenes

In this reaction, the two product formed are not in equal proportions. The reaction at the two ends is not equal because of the formation of a unsymmetrical aromatic radical. Thus, the reaction at the primary end (which is less hindered) is favoured.

Bromination of 5-methylcyclohept-1-ene

Bromination of 5-methylcyclohept-1-ene with NBS results in the formation of two products i.e. 3-bromo-5-methylcycloheptene and 3-bromo-6 methylcycloheptene.

The reaction is given below: