Hi Sourav.

Etard Reaction is an organic reaction of methyl benzene. In this reaction, the Benzene ring undergoes an oxidation reaction and becomes an Aldehyde group. Etard reaction usually involves Chromyl Chloride as the oxidizing agent.

Reaction Example1: Toulene oxidation to produce Benzaldehyde

C6H5-CH3 -------> C6H5-COH

The Mechanism for it is basic Oxidation mechanism.