For different halogens, the active order of substitution reaction with benzene ring is fluorine>chlorine>bromine>iodine. Due to the excessive activity of fluorine, direct reaction with benzene will cause the benzene ring to break. Benzene and xenon difluoride can generate fluorobenzene under the catalysis of hydrogen fluoride. The reaction between iodine and benzene is not only slow, but also generates hydrogen iodide as a reducing agent, making the reaction reversible and dominated by a reverse reaction.

By appropriately increasing the reaction temperature, halobenzenes can continue to react with halogens to generate dihalobenzenes, with the main products being ortho and para substituents. Alkylbenzene reacts with halogens under similar conditions, and the reaction is easier than benzene, mainly resulting in ortho and para substituents.

It is difficult to carry out the substitution reaction between benzene and halogen without catalyst. So, simply mixing benzene with carbon tetrachloride solution of bromine makes it difficult for the two to react. Under the action of catalysts such as FeX2, AlCl3, and other Lewis acids, benzene can quickly react with chlorine or bromine to form chlorobenzene or bromobenzene.