Question

Benzaldehyde is liquid at normal temperature and pressure usually is solid deposit at the neck of benzaldehyde bottle . Why

Answer 1

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 oxidised to benzoic acid.

Benzoic acid is a white solid particle which then gets accumulated at the neck of the bottle.