Question

Which product will be formed during Etard’s reaction?

• A. Benzoic acid
• B. Benzyl alcohol
• C. Benzaldehyde
• D. Benzene

Hint:

Etard's reaction is highly selective. Chromyl chloride ($CrO_2Cl_2$) acts as a controlled oxidizing agent that arrests the oxidation at the aldehyde stage ($C_6H_5CHO$), preventing further oxidation into benzoic acid.

Answer 1

The Correct Option is C

Step 1: Recall Etard's reaction.
This reaction turns a methyl group on a benzene ring into an aldehyde. The reagent is chromyl chloride, $CrO_2Cl_2$, used in $CCl_4$.

Step 2: First stage.
Toluene reacts with chromyl chloride to form a brown chromium complex:
\[ C_6H_5CH_3 + 2CrO_2Cl_2 \rightarrow C_6H_5CH(OCrOHCl_2)_2 \]

Step 3: Break the complex.
Adding water hydrolyses this brown solid and releases the aldehyde:
\[ C_6H_5CH(OCrOHCl_2)_2 \xrightarrow{H_3O^+} C_6H_5CHO \]
The oxidation stops here and does not move on to benzoic acid.

Step 4: Name the product.
The final product is benzaldehyde.
\[ \boxed{\text{Benzaldehyde}} \]