Which of the following compounds react with aldehyde to form Schiff's base? (a) \(1^{\circ}\) amines (b) \(2^{\circ}\) amines (c) \(3^{\circ}\) amines (d) amides

Schiff's base is formed by the reaction between an aldehyde (or a ketone) and a primary amine. The mechanism of this reaction involves the nucleophilic attack of the nitrogen atom in the amine on the carbonyl carbon atom of the aldehyde, followed by the elimination of water to form an imine group.

We have the following options to consider: (a) \(1^{\circ}\) amines: Primary amines have the general formula R-NH2, where R is an alkyl or aryl group. Primary amines have one alkyl or aryl group bonded to the nitrogen atom and can undergo a nucleophilic attack on the carbonyl group of an aldehyde. (b) \(2^{\circ}\) amines: Secondary amines have the general formula R1R2NH, where R1 and R2 can be alkyl or aryl groups. Secondary amines have two alkyl or aryl groups bonded to the nitrogen atom, making them less nucleophilic and hence less reactive with aldehydes to form Schiff's bases. (c) \(3^{\circ}\) amines: Tertiary amines have the general formula R1R2R3N, where R1, R2 and R3 can be alkyl or aryl groups. Tertiary amines have three alkyl or aryl groups bonded to the nitrogen atom and are not nucleophilic, so they cannot form Schiff's bases with aldehydes. (d) amides: Amides have the general formula R-CO-NH2. The nitrogen atom in an amide is bonded to a carbonyl group, making it less nucleophilic and less likely to form Schiff's bases with aldehydes.

Based on the analysis of the given options, we can identify that primary amines (\(1^{\circ}\) amines) are the most suitable candidates to react with an aldehyde to form a Schiff's base. So the correct answer is (a) \(1^{\circ}\) amines.