Question

Reaction by which Benzaldehyde cannot be prepared

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is D

To solve the question of which reaction cannot be used to prepare Benzaldehyde, we need to consider each of the provided options and determine their compatibility with the formation of Benzaldehyde.

Option A: Rosenmund Reduction - This is a reduction process of acyl chlorides using Pd/BaSO₄ to form aldehydes, including Benzaldehyde.

Option B: Etard Reaction - This involves the oxidation of toluene to form Benzaldehyde. This is a valid method for preparing Benzaldehyde.

Option C: Gattermann-Koch Reaction - This method involves the treatment of benzene with CO and HCl in the presence of a catalyst to form benzaldehyde, thus viable for Benzaldehyde synthesis.

Option D: Cannizzaro Reaction - This is a redox reaction that takes place with aldehydes that do not contain α-hydrogen, such as Benzaldehyde, resulting in no isolation of Benzaldehyde due to its further reduction and oxidation. Therefore, this method cannot be used to prepare Benzaldehyde.

In conclusion, the reaction mentioned in Option D (Cannizzaro Reaction) is not suitable for preparing Benzaldehyde, as it leads to the disproportionate reaction of two aldehyde molecules, producing a carboxylic acid and an alcohol.