what happens when benzene is treated with Br2 in presence of anhydrous AlCl3​

When benzene is treated with bromine (Br2) in the presence of anhydrous aluminium chloride (AlCl3), a substitution reaction occurs. This reaction is known as electrophilic aromatic substitution. Here are the steps:

1. Generation of Electrophile: The first step is the generation of the electrophile. Bromine (Br2) reacts with anhydrous AlCl3 to form a complex, which is a powerful electrophile. The reaction is as follows: Br2 + AlCl3 → [Br-Br]+AlCl4-

2. Formation of sigma complex: The electrophile [Br-Br]+ then attacks the benzene ring to form a sigma complex. This step involves the breaking of the aromaticity of the benzene ring.

3. Deprotonation: The sigma complex then loses a proton to the AlCl4- ion to regenerate the AlCl3 catalyst and restore the aromaticity of the benzene ring. The final product is bromobenzene.

So, the overall reaction is: C6H6 + Br2 → C6H5Br + HBr in the presence of AlCl3.