In Etard reaction, the final product is

The correct option is Aromatic aldehyde.

Step-by-step explanation:

The Etard reaction is a well-known organic reaction used for the selective oxidation of a methyl group attached to an aromatic ring to produce an aldehyde. A classic example is the conversion of toluene to benzaldehyde.

1. Formation of the Chromium Complex:
In this reaction, the aromatic compound containing a methyl group (like toluene) is reacted with chromyl chloride:

$${\mathrm{CrO}}_2{\mathrm{Cl}}_2$$

in an inert solvent such as carbon disulfide (CS₂) or chloroform (CHCl₃). Chromyl chloride partially oxidizes the methyl group to form a brown-colored chromium complex intermediate.

2. Acid Hydrolysis:
The intermediate chromium complex is then decomposed using aqueous acid (hydrolysis). This step cleaves the intermediate complex to yield the final product, which is an aromatic aldehyde, along with chromium salts.

Reaction Equation Summary:
Ar-CH₃ + 2 CrO₂Cl₂ → Chromium Complex Intermediate → Ar-CHO (Aromatic Aldehyde)
where Ar represents an aromatic ring. Thus, the reaction selectively stops at the aldehyde stage without further oxidation to a carboxylic acid, making aromatic aldehyde the final product.