Given below are two statements:
Statement I : Vanilin
will react with NaOH and also with Tollen's reagent.
Statement II : Vanilin
will undergo self aldol condensation very easily.
In the light of the above statements, choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Read vanillin group by group: an acidic phenol, a free CHO, and not a single α-hydrogen.

1. Name the groups. Vanillin is 4-hydroxy-3-methoxybenzaldehyde. It has a phenolic -OH, a methoxy group and a -CHO attached directly to the benzene ring.

   Feature	Reagent or reaction	What happens
   Phenolic -OH	NaOH	Phenol is acidic, so it forms the sodium phenoxide: reacts
   -CHO group	Tollens' reagent	Aldehyde is oxidised to -COOH and a silver mirror forms: reacts
   α-carbon of -CHO	Self aldol condensation	The α-carbon is a ring carbon with no H, so no enolate forms: no aldol

2. Why no aldol. Aldol needs a base to pull an α-hydrogen off and make an enolate. In vanillin the carbon next to C=O is part of the benzene ring and carries no hydrogen, so vanillin cannot self-condense, just like benzaldehyde.
3. So. Statement I is correct and Statement II is incorrect, which is option (a).

The idea to keep. Before you say aldol, find the α-carbon and check it for hydrogen. Aldehydes with CHO on a benzene ring have none, so they cannot self-condense, but they still give Tollens' test.

Answer from the NTA final answer key. Solution by PrepWiser.