The bromination of toluene is the addition of bromine to toluene. This reaction occurs during halogenation, and it is activated by fluorination and chlorination. The cycle of halogenation ends with iodination.
Halogenation is the reaction of a halogen with another compound, and it occurs when a halogen — iodine, fluorine, bromine and chlorine — replaces at least one hydrogen atom in the compound. The cycle can occur with a variety of compounds, and the entire cycle is deemed as a complete chain propagation, beginning with fluorination and ending with iodination. The energy exuded for each reaction in the chain to occur varies as well as the energy yielded. In terms of bromination, it is less reactive than the stages of fluorination and chlorination, producing a lower activation energy than the two.