Question

benzaldehyde is liquid at normal temperature and pressure but usually a solid is deposit at the neck of benzaldehyde bottle.what this solid is and how it gets formed ? discuss the appropriate chemistry involved in the reaction​

Answer 1

The solid at the neck of benzaldehyde bottles is benzoic acid.

• Benzaldehyde is liquid in nature. When one repeatedly pours it out of the bottle, some of the liquid remains attached to the neck of the bottle.
• This liquid then comes in contact with air and undergoes aerial oxidation to form the white solid called benzoic acid.

Answer 2

Benzoic Acid

Explanation:

• The solid deposited at the neck of benzaldehyde bottles is benzoic acid
• Benzaldehyde is liquid at normal temperature and pressure When one repeatedly pours it out of the bottle, but usually a solid is accumulated around the neck of the benzaldehyde bottle as the liquid comes in contact with air and undergoes aerial oxidation forming the white solid crystals of benzoic acid
• Benzaldehyde readily undergoes autoxidation to form benzoic acid on exposure to air at room temperature that can be explained by Cannizzaro reaction

In the case of benzaldehyde, the Cannizzaro reaction can be applied to understand the above situation  -

1. Hydroxyl molecule from the air reacts with the benzaldehyde molecule
2. The hydride is transferred to the Carbonyl Carbon n benzaldehyde and a proton is transferred to the carbonyl oxygen
3. Cannizzaro reaction, which is a redox reaction occurs in which 2 molecules of  benzaldehyde is reduced and oxidized to benzyl alcohol and benzoic acid respectively

∴ Benzoic acid is a white solid particle that gets accumulated at the neck of the bottle.