Amines

part 1

Structure and Preparation

• Classification and nomenclature of amines
• Structure of amines
• Preparation from nitro compounds, nitriles, amides
• Gabriel phthalimide synthesis
• Hofmann bromamide degradation

part 2

Physical and Chemical Properties

• Physical properties of amines
• Basic character of amines
• Basicity order of amines
• Alkylation and acylation reactions
• Reactions with HNO₂ (diazotisation)

part 3

Diazonium Salts and Aromatic Amines

• Diazonium salts — preparation and properties
• Reactions of diazonium salts — Sandmeyer, Gattermann
• Coupling reactions
• Distinction between primary, secondary, tertiary amines

Basicity order

Aliphatic: 2° > 1° > 3° > NH₃; Aromatic: NH₃ > aniline

★ board favourite

Carbylamine reaction (ID test for 1° amine)

RNH₂ + CHCl₃ + 3KOH → RNC (isocyanide, foul smell)

★ board favourite

Diazonium salt formation (Sandmeyer)

ArNH₂ + NaNO₂ + HCl → ArN₂⁺Cl⁻ → ArCl (with CuCl)

★ board favourite

Structure of amines: sp³ N with lone pair

Pyramidal shape; lone pair responsible for basic character

★ frequently asked

Resonance of aniline (reduced basicity)

Lone pair delocalised into ring; less available for protonation

★ frequently asked

Gabriel phthalimide synthesis (primary amine)

Phthalimide + KOH → K-salt + RX → N-alkyl phthalimide → (H₂NNH₂) 1° amine

★ frequently asked

Hoffmann bromamide degradation

RCONH₂ + Br₂ + 4NaOH → RNH₂ + Na₂CO₃ + 2NaBr + 2H₂O

★ frequently asked

Azo dye coupling reaction

ArN₂⁺ + ArOH (alkaline) → Ar−N=N−Ar (coloured azo dye)

★ frequently asked

How will you distinguish between primary, secondary and tertiary amines using the Hinsberg reagent? Write the reactions involved.

Explain why aniline is a weaker base than ethylamine.

Arrange methylamine, dimethylamine, trimethylamine, and ammonia in increasing order of basic character in aqueous solution. Justify your answer.

(a) Write the reactions of benzene diazonium chloride with: (i) H₃PO₂ and water, (ii) CuCN, (iii) phenol (coupling). Name each reaction. (b) Why are diazonium salts of aromatic amines more stable than those of aliphatic amines?

Write the reaction for diazotization of aniline. What is the importance of diazonium salts in organic synthesis?

How are amines prepared by (i) Gabriel phthalimide synthesis and (ii) Hoffmann bromamide degradation reaction? Which method gives a pure primary amine and why?

What is the carbylamine reaction? Write the reaction and state its use as a test for primary amines.

Account for the following: (i) Aniline does not undergo Friedel–Crafts reaction. (ii) Aniline is acetylated before nitration. (iii) pKb of aniline is more than that of methylamine.

Arrange in decreasing order of basic strength in the gas phase: NH₃, CH₃NH₂, (CH₃)₂NH, (CH₃)₃N.

How will you convert: (i) aniline to benzonitrile, (ii) nitrobenzene to aniline? Write the reactions.

How many marks is Amines worth in the Class 12 board exam?

Around 6 marks of the 70-mark CBSE Chemistry theory paper, based on the official unit-wise weightage. Basicity order and diazotisation reactions — predict product.

Is Amines easy or hard?

It's rated hard — one of the tougher chapters in Class 12 Chemistry. Most students need about 3 hours to cover it well.

What are the important topics in Amines?

The chapter covers 11 NCERT topics in 3 areas: Structure and Preparation; Physical and Chemical Properties; Diazonium Salts and Aromatic Amines.

What questions come from Amines in board exams?

Between 2018–2024, CBSE board papers asked questions from this chapter on Distinction of Amines, Basicity, Basicity of Amines, Diazonium Salts — 1- to 5-mark questions.