The reaction between benzene and bromine in the presence of an iron catalyst is an example of electrophilic aromatic substitution, specifically bromination. The overall reaction can be represented as:C6H6 + Br2 C6H5Br + HBrThe mechanism of this reaction involves several steps:1. Formation of the electrophile:The iron catalyst usually FeBr3 reacts with bromine Br2 to form a complex, which generates the electrophile, the bromonium ion Br+ . The iron catalyst polarizes the bromine molecule, making one of the bromine atoms more electrophilic.FeBr3 + Br2 FeBr4- + Br+2. Electrophilic attack on benzene:The electrophilic bromine atom Br+ attacks the benzene ring, breaking one of the pi bonds and forming a sigma bond with a carbon atom. This results in the formation of a positively charged intermediate called a sigma complex or arenium ion. The aromaticity of the benzene ring is disrupted in this step.3. Deprotonation and regeneration of aromaticity:A base, usually the FeBr4- ion, abstracts a proton from the carbon atom that is bonded to the bromine atom in the sigma complex. This step restores the aromaticity of the benzene ring and generates the bromobenzene product.C6H5Br-FeBr4 C6H5Br + HFeBr44. Regeneration of the catalyst:The iron catalyst is regenerated when the HFeBr4 complex dissociates into FeBr3 and HBr, which can be used in further reactions.HFeBr4 FeBr3 + HBrIn summary, the iron catalyst plays a crucial role in the bromination of benzene by generating the electrophilic bromonium ion Br+ and facilitating the formation of the sigma complex. The reaction proceeds through an electrophilic aromatic substitution mechanism, with the formation of a sigma complex intermediate and the regeneration of the aromaticity in the final product, bromobenzene.