The reaction of benzene with HCl is an electrophilic aromatic substitution reaction. In this reaction, the hydrogen atom of HCl is replaced by a benzene ring. The reaction is catalyzed by a Lewis acid, such as aluminum chloride. The mechanism of the reaction is as follows:

1. The Lewis acid activates the HCl molecule, making it more electrophilic.

2. The benzene ring attacks the electrophilic HCl molecule, forming a Wheland intermediate.

3. The Wheland intermediate rearranges to form the final product, chlorobenzene.

The overall reaction can be represented as follows:

C6H6 + HCl → C6H5Cl + H2

The reaction of benzene with HCl is an important industrial process for the production of chlorobenzene. Chlorobenzene is used as a starting material for the production of a variety of other chemicals, including phenol, styrene, and DDT.