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Learn7405Paper 2 · Paper 2: Organic chemistryAminesAmines and nitriles
Amines · Subtopic 2 of 2

Amines and Nitriles

Amines contain N with a lone pair. Primary amines form when halogenoalkanes react with excess ammonia in ethanol, heated under pressure (excess limits further substitution to secondary and tertiary amines). Nitriles form from halogenoalkanes + KCN (ethanol) or carbonyls + HCN (hydroxynitriles); they can be hydrolysed (acid, reflux) to carboxylic acids or reduced (LiAlH₄, or H₂/Ni) to primary amines, giving an amine with one extra carbon and no mixture. Amines are bases: the N lone pair accepts H⁺, forming ammonium salts: RNH2+HCl→RNH3+Cl−\mathrm{RNH_2+HCl\rightarrow RNH_3^+Cl^-}.

Cambridge 9701 Paper 1Cambridge 9701 Paper 2Edexcel YCH11 WCH15AQA 7405 Paper 2≈ 40 minRevision 1 · updated 2026-10-30
Section 1 of 14

Learning objectives

  • Describe preparation of primary amines.
  • Explain why excess ammonia is used.
  • Describe nitrile hydrolysis and reduction.
  • Explain the basicity of amines.
Pause and think

Why does reacting bromoethane with ammonia give a mixture of products, while reducing ethanenitrile gives only ethylamine?

Section 2 of 14

Core idea

Start hereWhy lemon fixes fishy smells

Fish smells of amines. Lemon juice, an acid, turns them into salts that don't evaporate, so the smell goes.

The big idea

The lone pair on nitrogen makes amines bases and nucleophiles. Nitriles are a route to both acids and amines, adding one carbon to the chain.

1. Two routes to amines

Making primary amines

The nitrile route adds a carbon and gives a pure product.

Worked examplePlan a route

Make propylamine from chloroethane.

Goal
Reagents and intermediate.
Strategy
Propylamine has 3 C; chloroethane has 2: add a carbon.
  1. CH3CH2Cl+CN−→CH3CH2CN+Cl−\mathrm{CH_3CH_2Cl+CN^-\rightarrow CH_3CH_2CN+Cl^-}
    KCN in ethanol, reflux.
  2. CH3CH2CN+4[H]→CH3CH2CH2NH2\mathrm{CH_3CH_2CN+4[H]\rightarrow CH_3CH_2CH_2NH_2}
    LiAlH₄ in dry ether.
AnswerKCN then LiAlH₄, via propanenitrile.
✓ CheckCarbon count 2 → 3 ✓.
Key takeawayBase strength Alkyl groups push electrons onto N, so alkylamines are stronger bases than ammonia.

Summary

  • Excess NH₃ limits further substitution.
  • Nitrile: hydrolyse → acid; reduce → amine.
  • Amines + acid → ammonium salts.
Key words
Amine
Derivative of ammonia with alkyl/aryl groups on N.
Nitrile
Compound containing –C≡N.
Ammonium salt
Ionic product of an amine with an acid.
HistoryHofmann. August Wilhelm von Hofmann systematically studied amines in the 1850s; his student William Perkin accidentally made the first synthetic dye, mauveine, from an amine.
Fun factFishy smell. The smell of rotting fish comes from small amines like trimethylamine. Lemon juice reduces the smell by turning the amines into odourless salts.
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