Classifying and naming amines

Amines are relatives of ammonia, NH₃, in which one or more hydrogens have been replaced by carbon groups. Count the carbon groups on the nitrogen:

• Primary (1°): one carbon group, R–NH₂ (methanamine, CH₃NH₂).
• Secondary (2°): two, R₂NH (N-methylmethanamine, (CH₃)₂NH).
• Tertiary (3°): three, R₃N, with no H left on the nitrogen.

Notice that '1°, 2°, 3°' here means something different from alcohols: for amines it counts the groups on the nitrogen, not on a carbon.

Like ammonia, the nitrogen is sp³ hybridised and keeps a lone pair of electrons. The molecule is pyramidal, with the lone pair sitting on top. That lone pair is what makes amines bases and nucleophiles.

IUPAC names: replace the -e of the alkane with -amine, and give the position of the NH₂: ethanamine, propan-2-amine. Extra groups on the nitrogen get the prefix N-: CH₃CH₂NHCH₃ is N-methylethanamine. When the NH₂ is on a benzene ring, the compound is an aryl amine; the simplest is aniline, whose IUPAC name is benzenamine.

Isomers of amines can differ in the carbon chain, the position of the nitrogen, the groups attached to the nitrogen, or the class itself (1°, 2° or 3°) for the same molecular formula.