CBSE Class 12 Chemistry: Amines — Structure & Reactions Notes 2026

Classification of Amines

• Primary (1°): RNH₂; secondary (2°): R₂NH; tertiary (3°): R₃N
• Aliphatic (alkyl groups) and aromatic (aryl groups, e.g., aniline C₆H₅NH₂)
• Naming: prefix amino- or suffix -amine; N-methyl, N,N-dimethyl for 2° and 3°

Preparation of Amines

• Reduction of nitrobenzene: C₆H₅NO₂ + 6[H] → C₆H₅NH₂ + 2H₂O (Sn/HCl or Fe/HCl)
• Gabriel synthesis: produces 1° amine; potassium phthalimide + RX → N-alkylphthalimide → hydrolysis
• Hoffmann degradation: amide + Br₂ + KOH → 1° amine with one less carbon

Basic Character of Amines

• Amines are Lewis bases (donate lone pair); more basic than water
• Basicicity order: aliphatic 3° > 2° > 1° > NH₃ (in gas phase); 2° > 1° > 3° > NH₃ (in water — steric effect)
• Aniline less basic than aliphatic amines (lone pair delocalised into benzene ring)

Reactions of Amines

• With acids: R−NH₂ + HCl → R−NH₃⁺Cl⁻ (salt formation; soluble in water)
• Acylation: R−NH₂ + CH₃COCl → R−NHCOCH₃ + HCl (N-substituted amide)
• Carbylamine test (1° amines only): RNH₂ + CHCl₃ + KOH → R−NC (foul smell carbylamines)

Diazonium Salts

• Preparation: C₆H₅NH₂ + NaNO₂ + HCl at 0–5°C → C₆H₅N₂⁺Cl⁻
• Must be kept cold: unstable at room temperature
• Reactions: Sandmeyer reaction (ArCl, ArBr), coupling reaction with phenols/amines (azo dyes)

Coupling Reaction and Azo Dyes

• C₆H₅N₂⁺ + C₆H₅OH (alkaline) → C₆H₅−N=N−C₆H₄OH (orange/yellow azo dye)
• Azo dyes contain −N=N− chromophore; used in textile industry
• Congo red, methyl orange are examples of azo dyes

CBSE Exam — Amines

• Arrange aniline, N-methylaniline, N,N-dimethylaniline in order of basic strength with reasons
• Write reactions for: Gabriel synthesis to prepare propan-1-amine
• What is carbylamine test? Write equation for aniline