Organic Compounds Containing Nitrogen – JEE Chemistry Notes

Organic Compounds Containing Nitrogen

1. Introduction

Organic compounds containing nitrogen form a very important class of compounds. They include amines, cyanides, isocyanides, nitro compounds, and diazonium salts. These compounds show unique chemical behavior due to the presence of nitrogen.

2. Classification of Nitrogen Compounds

Class	Functional Group
Amines	$-NH_2,\,-NHR,\,-NR_2$
Nitro Compounds	$-NO_2$
Cyanides	$-CN$
Isocyanides	$-NC$
Diazonium Salts	$-N_2^+X^-$

3. Amines

3.1 Classification of Amines

Amines are classified based on the number of alkyl or aryl groups attached to nitrogen.

Type	General Formula
Primary (1°)	$RNH_2$
Secondary (2°)	$R_2NH$
Tertiary (3°)	$R_3N$

3.2 Preparation of Amines

Reduction of Nitro Compounds:
$RNO_2 \xrightarrow[\text{Sn/HCl}]{\text{or } H_2/Ni} RNH_2$

Gabriel Phthalimide Synthesis:
Used for preparation of primary amines only

Gabriel synthesis cannot produce secondary or tertiary amines.

3.3 Physical Properties of Amines

Lower amines are soluble in water due to hydrogen bonding. Boiling points increase with molecular mass.

3.4 Basic Nature of Amines

$RNH_2 + H_2O \rightleftharpoons RNH_3^+ + OH^-$

Order of basicity (aqueous):
$2^\circ > 1^\circ > 3^\circ > NH_3$

3.5 Chemical Reactions of Amines

Alkylation:
$RNH_2 + RX \rightarrow R_2NH$

Acylation (Schotten–Baumann reaction): $RNH_2 + RCOCl \rightarrow RNHCO R$

3.6 Tests for Amines

Carbylamine Test: Positive for primary amines only
Hinsberg Test: Differentiates 1°, 2°, and 3° amines

Carbylamine Reaction:
$RNH_2 + CHCl_3 + 3KOH \rightarrow RNC + 3KCl + 3H_2O$

4. Nitro Compounds

Nitro compounds contain the $-NO_2$ group attached to carbon. They are usually prepared by nitration of hydrocarbons.

$RH + HNO_3 \rightarrow RNO_2 + H_2O$

Nitro group shows strong electron withdrawing nature.

5. Cyanides and Isocyanides

5.1 Cyanides

$R-X + KCN \rightarrow R-CN$

Cyanides on hydrolysis give carboxylic acids.

5.2 Isocyanides

$RNH_2 + CHCl_3 + KOH \rightarrow R-NC$

Isocyanides have extremely unpleasant odor.

6. Diazonium Salts

Aromatic primary amines react with nitrous acid at $0–5^\circ C$ to form diazonium salts.

$ArNH_2 + NaNO_2 + HCl \rightarrow ArN_2^+Cl^- + 2H_2O$

6.1 Reactions of Diazonium Salts

Sandmeyer Reaction:
$ArN_2^+Cl^- + CuCl \rightarrow ArCl$

Replacement by OH:
$ArN_2^+Cl^- + H_2O \rightarrow ArOH$

7. Importance in JEE

Order of basicity questions are very common
Tests of amines appear frequently
Diazonium salt conversions are high scoring

8. Final Revision Checklist

You have mastered this chapter if you can:

Classify all nitrogen compounds correctly
Predict basic strength of amines
Identify amines using chemical tests
Write all reactions of diazonium salts
Differentiate cyanides and isocyanides