Preparation of Amines

Preparation of Primary Amines

1. Making of amines from halogenoalkanes

This process will be carried out in a sealed tube. Here haloalkanes will be heated with the concentrated solution of ammonia in ethanol. The mixture cannot be heated under the reflux as ammonia would move out in the form of gas from a container.

Now coming to the preparation of primary amine from halogenoalkane, the reaction takes place in two stages. Salt will be formed at the first stage. Here ethyl ammonium bromide is the salt. It is similar to ammonium bromide except for the fact that one of the hydrogens in the ammonium atom is replaced by an ethyl group.

A reverse reaction can occur between ammonia and the salt. It is illustrated in the above reaction.

2. Reduction of nitriles

We can get primary amines when nitriles are reduced with lithium aluminium hydride. This method is mainly used for the preparation of amines which contain one carbon atom more than the starting amine.

3. Gabriel phthalimide synthesis

We can get primary amines easily by Gabriel synthesis. In this process, on the treatment of phthalimide with ethanolic potassium hydroxide, we get potassium salts of phthalimide. When this is further heated with alkyl halide followed by alkaline hydrolysis then primary amine is produced. We cannot prepare aromatic primary amines because aryl halides do not undergo nucleophilic substitution with the anion which is formed by phthalimide.