Class 12 Chemistry – Amines: Classification

1. Amines Overview

• Amines are derivatives of ammonia (NH₃) where one or more hydrogen atoms are replaced by alkyl or aryl groups.

• Functional group: –NH₂ (amine group)

2. Classification of Amines

a) Primary Amines (1°)

• Definition: One hydrogen of ammonia is replaced by an alkyl or aryl group.

• General Concept: R–NH₂

• Features:

  • Contain one –NH₂ group attached to a carbon.

  • Usually more reactive and basic.

• Example Concept: Methylamine

b) Secondary Amines (2°)

• Definition: Two hydrogens of ammonia are replaced by alkyl or aryl groups.

• General Concept: R–NH–R’

• Features:

  • Contain one nitrogen bonded to two carbon atoms.

  • Less basic than primary amines.

• Example Concept: Dimethylamine

c) Tertiary Amines (3°)

• Definition: All three hydrogens of ammonia are replaced by alkyl or aryl groups.

• General Concept: R–N–R’R’’

• Features:

  • Nitrogen bonded to three carbon atoms.

  • Least basic among aliphatic amines.

• Example Concept: Trimethylamine

d) Aromatic Amines

• Definition: Amines in which –NH₂ is attached to an aromatic ring (like benzene).

• General Concept: Ar–NH₂

• Features:

  • Lone pair on nitrogen is delocalized into the ring, reducing basicity.

  • Less reactive than aliphatic amines.

• Example Concept: Aniline

3. Quick Comparison Table

4. Key Points to Remember

• Primary, secondary, tertiary: Based on number of hydrogens replaced by carbon groups.

• Aromatic amines: Special case; nitrogen attached to benzene ring.

• Basicity trend (aliphatic): 1° > 2° > 3°

• Aromatic amines are less basic due to resonance delocalization.

• Amines are important in dyes, pharmaceuticals, and chemical synthesis.