Question

Why Anhydrous ${\mathrm{AlCl}}_3$ is used in Friedel Crafts reaction?

Answer 1

1. Anhydrous ${\mathrm{AlCl}}_3$ is used as a catalyst in Friedel Craft reactions.
2. Friedel Craft reactions are reactions involve thee attack on electrophile on the aromatic ring. It is an electrophilic substitution reactions.
3. Two primary types of Friedel Craft reactions are Friedel Craft alkylation and Friedel Craft acylation.
4. In Friedel Craft Alkylation attack of alkyl group ${\mathrm{CH}}_3$ on aromatic ring takes place whereas in Friedel Craft acylation attack of acetyl group ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CO}$ takes place.
5. Anhydrous ${\mathrm{AlCl}}_3$ is used as a catalyst in Friedel Craft reactions as it is an electron -deficient species and acts as Lewis acid.
6. ${\mathrm{AlCl}}_3$ accepts ${\mathrm{Cl}}^{-}$ from the incoming electrophile and becomes ${\mathrm{AlCl}}_{{}_4}^{-}$.Then attack of electrophile becomes easy.