Preparation of Aliphatic & Aromatic Amines

This lesson covers: 

  1. How aliphatic amines are produced
  2. The reaction mechanism involved in producing aliphatic amines
  3. How aromatic amines are produced

Reacting halogenoalkanes with ammonia and amines

Aliphatic amines can be produced by reacting a halogenoalkane with ammonia, primary amines, or secondary amines in a nucleophilic substitution reaction.


  1. Reaction with ammonia to form primary amines:

Primary aliphatic amines can be produced by heating a halogenoalkane with excess ethanolic ammonia.

For example, bromoethane reacts with ammonia to give ethylamine:

CH3CH2Br + 2NH3 ➔ CH3CH2NH2 + NH4Br


  1. Reaction with primary amines to form secondary amines:

Secondary aliphatic amines can be produced by reacting a halogenoalkane with a primary amine.

For example, bromoethane reacts with ethylamine to give diethylamine:

CH3CH2NH2 + CH3CH2Br ➔ (CH3CH2NH2)2NH + HBr


  1. Reaction with secondary amines to form tertiary amines:

Tertiary aliphatic amines can be produced by reacting a halogenoalkane with a secondary amine.

For example, bromoethane reacts with diethylamine to give triethylamine:

(CH3CH2)2NH + CH3CH2Br ➔ (CH3CH2)3N + HBr

Mechanism of amine formation

The nucleophilic substitution mechanism for these reactions involves two steps:

  1. The nucleophile (ammonia or amine) attacks the halogenoalkane, displacing the halogen and forming an alkylammonium salt.
  2. The alkylammonium salt is then deprotonated by a base (e.g., the nucleophile or a separate base) to form the amine product.


For example, the mechanism for the reaction between bromoethane and ammonia is:

Diagram showing the nucleophilic substitution mechanism for the reaction between bromoethane and ammonia.

Aromatic amines from nitro compounds

Aromatic amines are produced by reducing nitro compounds in a two-step process:

  1. The nitro compound is heated under reflux with tin and concentrated HCl to form an ammonium salt.
  2. The ammonium salt is then treated with aqueous NaOH to give the free amine.


For example, nitrobenzene is reduced to phenylamine via phenylammonium chloride:

Chemical reaction showing the reduction of nitrobenzene to phenylamine using tin, concentrated HCl, and aqueous NaOH.

Aromatic amines like this are useful in organic synthesis for making pharmaceuticals, dyes, and other compounds.