Chemistry · Amines · NEET
Yes for NEET. When a primary amine reacts with an aldehyde or ketone, the C=N product (R-CH=N-R') is called an imine. When R' on the nitrogen is a carbon group (not just hydrogen), that imine is also called a Schiff base. NCERT uses both words for the same product, so treat 'Schiff base' and 'imine' as the same answer.
The nitrogen lone pair first adds to the carbonyl carbon, giving an unstable intermediate called a carbinolamine (also written as hemiaminal, R-CH(OH)-NH-R'). This has both an -OH and an -NH on the same carbon. To become stable, it removes one molecule of water, and the leftover atoms form a strong C=N double bond. So water leaving is the step that creates the imine.
No. A secondary amine (R2NH) has no second hydrogen on nitrogen to lose along with the -OH, so it cannot form a C=N double bond. Instead it forms an enamine (C=C-N). Only primary amines give a true imine or Schiff base with an aldehyde. NEET often tests this difference.
No. This is a condensation, not an oxidation. The carbonyl carbon keeps its oxidation state; oxygen is simply replaced by nitrogen and water leaves. So the answer is never a ketone, carboxylic acid, or aromatic acid. Students who pick 'carboxylic acid' fall for this trap.
A trace of acid speeds up the reaction by protonating the -OH of the carbinolamine, turning it into water, which is a good leaving group. But too much acid protonates the amine's lone pair (making R-NH3+), so it can no longer attack the carbonyl. That is why imine formation works best at mild, slightly acidic pH.
The product formed by the reaction of an aldehyde with a primary amine is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
An imine, R-CH=N-R', commonly called a Schiff base, plus one molecule of water.
Two molecules join and a small molecule (water) is removed. Joining plus loss of water is called condensation.
Yes. A ketone with a primary amine gives R2C=N-R', but ketones react more slowly than aldehydes because they are less reactive and more crowded.
It is called a carbinolamine or hemiaminal, R-CH(OH)-NH-R'. It has both -OH and -NH on the same carbon and is unstable.
It is a one-mark reaction that NEET has directly asked, and it also appears inside multi-step conversion questions. Knowing the C=N product and that it is not an oxidation avoids common mistakes.
