Question

Toluene on treatment with chromic oxide in acetic anhydride at 273K to 283K gives

• A. benzaldyde
• B. benzylidene diacetate
• C. benzoic acid
• D. benzyl alcohol
• E. phenylacetate

Answer 1

The Correct Option is B

When toluene is treated with chromic oxide (CrO\(_3\)) in acetic anhydride at a temperature range of 273K to 283K, the methyl group (–CH\(_3\)) on the benzene ring undergoes oxidation. The reaction leads to the formation of benzylidene diacetate, which results from the formation of a C=O group and the addition of the acetic anhydride. In contrast, benzaldehyde, benzoic acid, and other options are not the products of this specific reaction under the given conditions.

The correct option is (B) : benzylidene diacetate

Answer 2

The reaction of toluene with chromic oxide (CrO₃) in acetic anhydride at 273K to 283K is known as the Étard reaction. This reaction selectively oxidizes the methyl group of toluene to an aldehyde.

In this specific case, the product formed is benzaldehyde, but it is isolated as benzylidene diacetate first.

The reaction proceeds as follows:

\(C_6H_5CH_3 + CrO_3(CH_3CO)_2O \rightarrow C_6H_5CH(OCOCH_3)_2 \)

Toluene reacts with chromic oxide in acetic anhydride to give benzylidene diacetate. This is then hydrolyzed to produce benzaldehyde.

\(C_6H_5CH(OCOCH_3)_2 + H_2O \rightarrow C_6H_5CHO + 2CH_3COOH\)

Therefore, Toluene on treatment with chromic oxide in acetic anhydride at 273K to 283K gives benzylidene diacetate. Then hydrolysis occurs to give benzaldehyde.

Therefore, the answer is benzylidene diacetate.