Playbook
Amines
Basicity, preparation, the tests that tell the classes apart, and diazonium salts with their replacement and coupling reactions.
- Questions in the bank
- 160
- q/paper in 2025–26
- 1.34
- Calculation
- 19%
- Notes pages
- 8
Strand: Reactions
When you’ll see it
A nitrogen base is ranked by basicity, made or degraded, tested by carbylamine or Hinsberg, or turned into a diazonium salt or an azo dye.
How this chapter is tested
Everything turns on one lone pair: how freely it takes a proton, how strongly it activates a benzene ring, and what becomes of the nitrogen once it is a diazonium ion. Basicity orders, ring substitution on aniline and the diazonium replacements all follow from that.
Multistep sequences are common, so learn each reagent with the carbon count and ring position it leaves behind. Hofmann bromamide removes a carbon, reduction of a nitrile from RX + KCN adds one, Gabriel gives only primary alkyl amines.
The numbers are short stoichiometry: grams of acetanilide or dye from a mass of aniline, litres of N₂ from an aliphatic amine and nitrous acid, the nitrogen content of a product, or how many amines in a list pass a test. One mole of amine gives one mole of each product, so the work is the molar masses.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Basicity
In water: (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃ but (C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂ > NH₃; aniline is weak, benzylamine aliphatic-strength; amides and pyrrole barely basic.
Preparation
Sn/HCl or Fe/HCl on ArNO₂; LiAlH₄ on RCN or RCONH₂ keeps every carbon; ammonolysis gives a mixture unless NH₃ is in excess; Gabriel gives pure 1° alkyl amines, never aryl.
Hofmann bromamide degradation
RCONH₂ + Br₂ + 4NaOH → RNH₂ + Na₂CO₃, through an isocyanate; one carbon shorter; aryl groups migrate too; ring positions are kept.
Acylation, nitrous acid and Hofmann elimination
Acetylation adds 42 g/mol per acetylated N; 1° aliphatic amine + HNO₂ → alcohol + N₂; quaternary hydroxide on heating gives the less substituted alkene.
Carbylamine and Hinsberg tests
CHCl₃/alc. KOH gives an isocyanide from any 1° amine; C₆H₅SO₂Cl: 1° product dissolves in alkali, 2° precipitates, 3° does not react.
Ring substitution on aniline
Bromine water → 2,4,6-tribromoaniline; acetylate first for one Br; direct nitration gives much meta via the anilinium ion; Friedel–Crafts fails; heating with H₂SO₄ → sulphanilic acid.
Diazonium salts and replacements
ArNH₂ + NaNO₂/HCl at 273–278 K; CuCl, CuBr, CuCN (Sandmeyer); KI → ArI; HBF₄ then heat → ArF; warm water → phenol; H₃PO₂ or ethanol → ArH.
Coupling and azo dyes
Phenol in mild alkali → orange 4-hydroxyazobenzene; aniline in mild acid → aniline yellow; β-naphthol → orange-red dye; attack para to OH or NH₂; moles of dye = moles of diazonium salt.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the ones that cut across chapters.
Tertiary as the strongest base in water
Tertiary wins only in the gas phase. In water solvation and crowding pull it back, and the methyl and ethyl series give different orders.
Benzamide to benzylamine
Hofmann bromamide removes the carbonyl carbon: C₆H₅CONH₂ gives aniline. Benzylamine comes from LiAlH₄ on the same amide.
NH₂ called a meta director
The amino group directs ortho-para. The meta nitroaniline from direct nitration comes from the anilinium ion formed in the acid.
Benzylamine treated as aryl
Its nitrogen is on a CH₂, so it is strongly basic, gives N₂ and benzyl alcohol with nitrous acid, and forms no stable diazonium salt or azo dye.
Fluoro- and iodoarenes from copper
Copper(I) salts deliver Cl, Br and CN only. Iodobenzene comes from KI, fluorobenzene from the fluoroborate on heating, and ethanol on a diazonium salt gives benzene, not an ether.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a mastery check for each page. Read the notes once, then drill page by page below.
Amines notesDrill every Amines question
160 questions from the bank, across 8 subtopics.
Drill one subtopic at a time
The 8 subtopics, in teaching order.
- Structure, Physical Properties and BasicityDrill Structure, Physical Properties and Basicity
- Preparation: Reduction, Ammonolysis and Gabriel SynthesisDrill Preparation: Reduction, Ammonolysis and Gabriel Synthesis
- Hofmann Bromamide DegradationDrill Hofmann Bromamide Degradation
- Acylation, Nitrous Acid and Hofmann EliminationDrill Acylation, Nitrous Acid and Hofmann Elimination
- Carbylamine and Hinsberg TestsDrill Carbylamine and Hinsberg Tests
- Electrophilic Substitution in AnilineDrill Electrophilic Substitution in Aniline
- Diazonium Salts: Stability and Replacement ReactionsDrill Diazonium Salts: Stability and Replacement Reactions
- Coupling Reactions and Azo DyesDrill Coupling Reactions and Azo Dyes
Related playbooks
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