amino group, in chemistry, functional group that consists of a
nitrogen atom attached by single bonds to hydrogen atoms, alkyl
groups, aryl groups, or a combination of these three. An organic
compound that contains an amino group is called an amine. Amines
are derivatives of the inorganic compound ammonia, NH3. When
one, two, or all three of the hydrogens in ammonia are replaced
by an alkyl or aryl group, the resulting compound is known as a
primary, secondary, or tertiary amine, respectively. Like
ammonia, the amines are weak bases because the unshared electron
pair of the nitrogen atom can form a coordinate bond with a
proton (see chemical bond). Amines will react with a mineral
acid to form an amine salt, e.g., with hydrochloric acid to form
an amine hydrochloride. A water-insoluble amine can be made to
dissolve by adding acid to form its water-soluble amine salt.
Amines react similarly with alkyl halides to form alkyl ammonium
salts. Amines can be synthesized by reacting ammonia with an
alkyl halide and n