A detail reaction mechanism that is operative during the reaction methane and bromine gas is shown below.
In present mechanism, Br2 undergoes homolytic bond fission under irradiation with UV light. This results in generation of two Br· free radicals.
This, this free radical abstracts H· from methane to form HBr. This process in turn generates methyl radical.
Methyl radical combines with other Br· to form bromomethane.
UV irritation in present reaction systems, initiates chain of events
