Does radical halogenation only occur in alkanes?
But there are differences.
If you use
Instead, you use NBS (N-bromosuccinimide) in
NBS is insoluble in
Then the bromine molecules are homolytically cleaved by light to produce the bromine radicals that initiate the reaction.
The second difference is that the substitution occurs almost exclusively at the allylic position.
Allylic bromination is the only practical method for laboratory free radical halogenation.
But allylic chlorination with low concentrations is important in industry, where the reaction is carried out at high temperature.