Question

Which of the following reaction does not form benzaldehyde as product?

• A. Rosenmund reaction
• B. Etard reaction
• C. Gattermann Koch reaction
• D. Cannizzaro reaction

Hint:

Cannizzaro converts aldehydes into alcohol + acid — not aldehyde formation.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Several named reactions are specifically designed for the synthesis of aldehydes. We need to distinguish between synthesis reactions and reactions where the aldehyde is a reactant.
Step 3: Detailed Explanation:
1. Rosenmund reaction: Hydrogenation of benzoyl chloride using $H_{2}/Pd-BaSO_{4}$ produces benzaldehyde.
2. Etard reaction: Oxidation of toluene using chromyl chloride ($CrO_{2}Cl_{2}$) produces benzaldehyde.
3. Gattermann Koch reaction: Reaction of benzene with $CO$ and $HCl$ in the presence of $AlCl_{3}$ produces benzaldehyde.
4. Cannizzaro reaction: This is a disproportionation reaction of an aldehyde that lacks an $\alpha$-hydrogen. Benzaldehyde itself is the reactant in this process. When treated with concentrated $NaOH$, one molecule of benzaldehyde is reduced to benzyl alcohol and another is oxidized to sodium benzoate. It does not form benzaldehyde as a product; it consumes it.
Step 4: Final Answer:
The Cannizzaro reaction does not form benzaldehyde as a product.