Mechanism of Gattermann Reaction

The mechanism of the Gattermann Reaction involves the following steps:

1. Formation of the Formyl Cation: The HCN reacts with HCl to form the formyl cation (H⁺-C≡N).
2. Activation of the Aromatic Ring: The aromatic compound reacts with the Lewis acid (AlCl₃ or CuCl) which activates it towards electrophilic substitution.
3. Electrophilic Attack: The formyl cation then attacks the activated aromatic ring, leading to the formation of an intermediate complex.
4. Deprotonation: The intermediate complex loses a proton (H⁺) to form the final aromatic aldehyde product.

This stepwise mechanism helps in understanding how the formyl group is introduced into the aromatic ring, making the Gattermann Reaction a valuable tool in organic synthesis.