benzaldehyde is liquid at normal temperature and pressure but usually a solid is deposited at the neck of benzaldehyde bottle
Answers
Answer:
Benzaldehyde is a simple aldehyde molecule which undergoes the Cannizzaro reaction to form benzoic acid.
Cannizzaro reaction refers to a redox reaction, wherein 2 molecules of the aldehyde react with each other to yield a primary alcohol and a carboxylic acid molecule.
In the case of benzaldehyde;
Step 1: Hydroxyl molecule from the air reacts with the benzaldehyde molecule
Step 2: The hydride is transferred to the Carbonyl Carbon n benzaldehyde and a proton is transferred to the carbonyl oxygen.
Step 3: Cannizzaro reaction, which is a redox reaction occurs wherein one molecule of benzaldehyde is reduced to benzyl alcohol and another molecule is oxidized to benzoic acid.
Benzoic acid is a white solid particle which then gets accumulated at the neck of the bottle.
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 -
- Hydroxyl molecule from the air reacts with the benzaldehyde molecule
- The hydride is transferred to the Carbonyl Carbon n benzaldehyde and a proton is transferred to the carbonyl oxygen
- 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.