The reactions of amines with water

The reactions of amines with water

Again, it is easiest to use the Bronsted-Lowry theory and, again, it is useful to do a straight comparison with ammonia.

A reminder about the ammonia reaction with water

Ammonia is a weak base and takes a hydrogen ion from a water molecule to produce ammonium ions and hydroxide ions.

However, the ammonia is only a weak base, and doesn't hang on to the hydrogen ion very successfully. The reaction is reversible, with the great majority of the ammonia at any one time present as free ammonia rather than ammonium ions.

The presence of the hydroxide ions from this reaction makes the solution alkaline.

The corresponding reaction with amines

The amine still contains the nitrogen lone pair, and does exactly the same thing.

For example, with ethylamine, you get ethylammonium ions and hydroxide ions produced.

There is, however, a difference in the position of equilibrium. Amines are usually stronger bases than ammonia. (There are exceptions to this, though - particularly if the amine group is attached directly to a benzene ring.)