Question

How Does AlCl₃ act as a Catalyst?

Answer 1

1. AlCl₃ (Aluminium chloride) is a strong Lewis acid, commonly used as a catalyst for halogenation (especially chlorination)of the aromatic group, it also leads to the creation of carbonation which is used in an electrophilic substitution reaction.
2. In the halogenation reaction, ${\mathrm{AlCl}}_3$ being a lewis acid coordinated to chlorine atom, thus break the ${\mathrm{Cl}}_2$ bond
3. Hence it will increase the electrophilicity of its binding partner making the binding partner more reactive.

The above points and diagram clearly explains the action of ${\mathrm{AlCl}}_3$ act as catalyst.