Question

formation of hexaclorobenze from benzene and excess of chlorine in dark is free radical addition reaction or free radical substitution reaction?​

Answer 1

Answer:

In the presence of ultraviolet light (but without a catalyst present), hot benzene will also undergo an addition reaction with chlorine or bromine. The ring delocalisation is permanently broken and a chlorine or bromine atom adds on to each carbon atom.

For example, if you bubble chlorine gas through hot benzene exposed to UV light for an hour, you get 1,2,3,4,5,6-hexachlorocyclohexane or benzenehexachloride.