CBSE Class 12 · Chemistry · NCERT Chemistry-II
Amines: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 27 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Classification
- Structure
- Basicity order
- Aromatic amines are weaker bases
- Preparation methods
- Reactions
- Diazonium salts
- Formulas and facts
- General formula of amines
- IUPAC naming
- Basicity order in gas phase
- Basicity in aqueous solution
- Reduction of nitro compounds
- Gabriel synthesis
- Hoffmann bromamide degradation
- Worked examples
- Naming an amine
- Comparing basicity
- Identifying an amine using the…
- Watch out for
- Thinking tertiary amines are most…
- Forgetting to keep temperature at…
- Confusing primary, secondary and…
- Applying Gabriel synthesis to…
- Writing the wrong carbon count in…
What this chapter is about
Amines are organic compounds derived from ammonia (NH₃) by replacing one, two or all three hydrogen atoms with alkyl or aryl groups. They are nitrogen-containing compounds that play a crucial role in biochemistry—proteins, alkaloids, vitamins and many pharmaceuticals contain amine groups. Understanding amines helps explain how drugs like antihistamines, local anaesthetics and sulfa drugs work.
Key ideas
- Classification: Amines are primary (1°), secondary (2°) or tertiary (3°) depending on whether one, two or three hydrogen atoms of NH₃ are replaced. A quaternary ammonium salt has four groups attached to nitrogen with a positive charge, such as (CH₃)₄N⁺Cl⁻.
- Structure: The nitrogen in amines has a lone pair and is sp³ hybridised, giving a pyramidal shape. This lone pair is responsible for the basic character and nucleophilic behaviour of amines.
- Basicity order: Aliphatic amines are more basic than ammonia, which is more basic than aromatic amines. In aqueous solution, the order is often: secondary > primary > tertiary for aliphatic amines, due to a balance between inductive effect and solvation.
- Aromatic amines are weaker bases: In aniline, the lone pair on nitrogen delocalises into the benzene ring (resonance), making it less available for accepting a proton.
- Preparation methods: Amines can be prepared by reduction of nitro compounds, ammonolysis of alkyl halides, Gabriel phthalimide synthesis (gives pure primary amines), Hoffmann bromamide reaction (converts amide to amine with one fewer carbon).
- Reactions: Amines undergo alkylation, acylation, reaction with nitrous acid (HNO₂), carbylamine reaction (isocyanide test for 1° amines), and electrophilic substitution in aromatic amines.
- Diazonium salts: Formed by treating aromatic primary amines with NaNO₂ and HCl at 0–5 °C. They are unstable but extremely versatile, undergoing Sandmeyer reaction, coupling reactions to form azo dyes, and replacement reactions.
Formulas and facts to remember
- General formula of amines: Primary amine R–NH₂, secondary amine R₂NH, tertiary amine R₃N.
- IUPAC naming: Replace the ending -e of the parent alkane with -amine. Example: CH₃–NH₂ is methanamine; C₆H₅–NH₂ is aniline (common) or benzenamine (IUPAC).
- Basicity order in gas phase: (CH₃)₃N > (CH₃)₂NH > CH₃NH₂ > NH₃ (inductive effect dominates).
- Basicity in aqueous solution: (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃ (solvation effect also matters).
- Reduction of nitro compounds: R–NO₂ + 3H₂ (Ni catalyst, or Sn/HCl, or Fe/HCl) → R–NH₂ + 2H₂O.
- Gabriel synthesis: Potassium phthalimide + R–X → N-alkylphthalimide; then hydrolysis with aqueous NaOH or hydrazine gives R–NH₂.
- Hoffmann bromamide degradation: R–CO–NH₂ + Br₂ + 4NaOH → R–NH₂ + Na₂CO₃ + 2NaBr + 2H₂O (amine has one carbon less).
- Diazotisation: C₆H₅–NH₂ + NaNO₂ + 2HCl (0–5 °C) → C₆H₅–N₂⁺Cl⁻ + NaCl + 2H₂O.
Common mistakes
- Thinking tertiary amines are most basic in water because they have three alkyl groups → in aqueous solution, solvation of the conjugate acid matters; secondary amines are often most basic.
- Forgetting to keep temperature at 0–5 °C during diazotisation → diazonium salts decompose at higher temperatures; always maintain ice-cold conditions.
- Confusing primary, secondary and tertiary amines with primary, secondary and tertiary carbons → amine classification is based on the number of carbon groups attached to nitrogen, not the carbon type.
- Applying Gabriel synthesis to prepare aromatic amines → aryl halides do not undergo nucleophilic substitution easily; Gabriel synthesis works only for primary aliphatic amines.
- Writing the wrong carbon count in Hoffmann bromamide reaction → the product amine has one carbon atom fewer than the starting amide.
Quick revision
- Amines are derivatives of NH₃; classified as 1°, 2° or 3° based on the number of C groups on N.
- Aliphatic amines are stronger bases than aniline because resonance in aniline delocalises the lone pair.
- Reduction of nitro compounds and Hoffmann bromamide degradation are key preparation methods.
- Carbylamine test (foul smell of isocyanide) identifies primary amines only.
- Diazonium salts are prepared below 5 °C and are starting points for Sandmeyer reaction and azo dye synthesis.
- In aqueous solution, basicity order of methyl-substituted amines: secondary > primary > tertiary > ammonia.