Final answer:
Halogenation of a benzene ring requires a halogen such as Cl₂ or Br₂ and a catalyst like FeCl₃, which facilitates the electrophilic aromatic substitution reaction.
Step-by-step explanation:
Halogenation of a benzene ring requires specific conditions due to the stability and unreactive nature of benzene. This stability comes from the delocalization of electrons in the aromatic system. To perform a halogenation reaction on benzene, you need a halogen such as chlorine (Cl₂) or bromine (Br₂) and the presence of a catalyst, typically iron (III) chloride (FeCl₃) for chlorination or iron bromide (FeBr₃) for bromination. This process is a classic example of an electrophilic aromatic substitution reaction, where a halogen atom replaces one of the hydrogen atoms on the benzene ring, resulting in an aryl halide. The iron catalyst enables the formation of a strong electrophile, which is necessary to react with the relatively stable benzene ring.