34.1 Primary and Secondary Amines

2026 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Recall the reactions (reagents and conditions) by which primary and secondary amines are produced:
    • (a) Reaction of halogenoalkanes with NH₃ in ethanol, heated under pressure
    • (b) Reaction of halogenoalkanes with primary amines in ethanol, heated in a sealed tube / under pressure
    • (c) Reduction of amides with LiAlH₄
    • (d) Reduction of nitriles with LiAlH₄ or H₂/Ni
  2. Describe the condensation reaction of ammonia or an amine with an acyl chloride at room temperature to give an amide
  3. Describe and explain the basicity of aqueous solutions of amines

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What Are Amines?

Amines are organic compounds that contain a nitrogen atom bonded to one or more carbon atoms (from a carbon chain) and/or hydrogen atoms. Think of amines as being derived from ammonia (NH₃) — where one or more of the hydrogen atoms in ammonia have been replaced by a carbon-containing group (called an alkyl group).

The type of amine depends on how many alkyl groups are attached to the nitrogen atom:

  • A primary amine has one alkyl group attached to nitrogen (and two hydrogen atoms on nitrogen). General formula: RNH₂
  • A secondary amine has two alkyl groups attached to nitrogen (and one hydrogen atom on nitrogen). General formula: R₂NH
  • A tertiary amine has three alkyl groups and no hydrogen atoms on nitrogen. General formula: R₃N (Note: tertiary amines are outside this syllabus objective but mentioned so you understand the pattern)

Example of a primary amine: Methylamine, CH₃NH₂ — one methyl group (CH₃) attached to nitrogen.

Example of a secondary amine: Dimethylamine, (CH₃)₂NH — two methyl groups attached to nitrogen.

Objective 1 — How Are Primary and Secondary Amines Made?

There are four key reactions you need to know for producing amines.

(a) Reaction of Halogenoalkanes with NH₃

A halogenoalkane (also called a haloalkane) is an alkane (carbon chain) where one or more hydrogen atoms have been replaced by a halogen atom (like Cl, Br, or I).

When a halogenoalkane reacts with ammonia (NH₃), a primary amine can be formed.

Reagents and Conditions:

  • Halogenoalkane + excess ammonia (NH₃)
  • Solvent: ethanol (this helps dissolve both reactants)
  • Heated under pressure (the reaction is done in a sealed container so the ammonia, which is a gas, cannot escape)

What happens in this reaction?

The nitrogen atom in NH₃ has a lone pair of electrons (a pair of electrons not used in bonding). This lone pair is attracted to the carbon atom that carries the halogen, because that carbon is slightly positive (the halogen pulls electrons away from it). The nitrogen attacks this carbon, the halogen leaves as a halide ion (e.g. Cl⁻, Br⁻), and a primary ammonium salt forms first. This salt then reacts with excess ammonia to release the primary amine as the product.

Example reaction:

CH₃Br + NH₃ → CH₃NH₂ + HBr

(Bromomethane reacts with ammonia to give methylamine — a primary amine)

Important note: If excess ammonia is not used, the primary amine that forms can itself react further with more halogenoalkane, producing a secondary amine, then a tertiary amine, and eventually a quaternary ammonium salt. Using excess ammonia keeps the main product as the primary amine.

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