Organic Compounds Containing Nitrogen

Master amines, diazonium salts, and their reactions for JEE Chemistry.

Nitrogen-containing organic compounds include amines, amides, nitriles, and diazonium salts.

Overview

graph TD
    A[Nitrogen Compounds] --> B[Amines]
    A --> C[Diazonium Salts]
    B --> B1[Classification]
    B --> B2[Reactions]
    C --> C1[Preparation]
    C --> C2[Reactions]

Amines

Classification

TypeStructureExample
Primary (1°)R-NH₂CH₃NH₂
Secondary (2°)R₂NH(CH₃)₂NH
Tertiary (3°)R₃N(CH₃)₃N

Basic Nature

Amines are Lewis bases (donate lone pair).

Basicity Order in Gas Phase: 3° > 2° > 1° > NH₃

Basicity Order in Aqueous Solution: 2° > 1° > 3° > NH₃ (for aliphatic)

For aromatic amines: Aniline < NH₃ (due to resonance)

Preparation

  1. Reduction of nitro compounds
  2. Hofmann bromamide reaction
  3. Gabriel phthalimide synthesis

Reactions

Acylation:

$$\text{RNH}_2 + \text{RCOCl} \rightarrow \text{RNHCOR} + \text{HCl}$$

Carbylamine Test (1° amine only):

$$\text{RNH}_2 + \text{CHCl}_3 + \text{3KOH} \rightarrow \text{RNC} + \text{3KCl} + \text{3H}_2\text{O}$$

Foul-smelling isocyanide formed.

Hinsberg Test:

  • 1° amine → Soluble sulfonamide
  • 2° amine → Insoluble sulfonamide
  • 3° amine → No reaction
JEE Tip
Use carbylamine test to distinguish 1° amines. Use Hinsberg test to classify 1°, 2°, and 3° amines.

Diazonium Salts

Preparation

$$\text{ArNH}_2 + \text{NaNO}_2 + \text{HCl} \xrightarrow{0-5°C} \text{ArN}_2^+\text{Cl}^-$$

Must be kept cold (< 5°C)

Reactions

Sandmeyer Reaction:

$$\text{ArN}_2^+ + \text{CuX} \rightarrow \text{ArX} + \text{N}_2$$

(X = Cl, Br, CN)

Gattermann Reaction:

$$\text{ArN}_2^+ + \text{Cu/HX} \rightarrow \text{ArX}$$

Other Substitutions:

ReagentProduct
H₃PO₂ArH (reduction)
KIArI
H₂O/H⁺ArOH
CuCNArCN

Coupling Reactions:

Diazonium salts couple with activated aromatic rings:

$$\text{ArN}_2^+ + \text{Ar'-H} \rightarrow \text{Ar-N=N-Ar'}$$

Forms azo dyes (colored compounds).

Importance in Synthesis

Diazonium salts are valuable intermediates for converting -NH₂ to other groups:

  • -NH₂ → -Cl, -Br, -I
  • -NH₂ → -CN → -COOH
  • -NH₂ → -OH
  • -NH₂ → -H

Practice Problems

  1. Arrange in order of basicity: aniline, methylamine, dimethylamine, ammonia

  2. How would you convert nitrobenzene to phenol?

  3. Explain the mechanism of diazotization.

Quick Check
Why must diazonium salts be prepared at low temperature?

Further Reading