Classification of Amines

Amines are classified along two independent axes. The first axis counts how many of ammonia's three hydrogen atoms have been replaced by an alkyl or aryl group: replace one hydrogen and the result is a primary (1 degree) amine, replace two and it is a secondary (2 degree) amine, replace all three and it is a tertiary (3 degree) amine (Table 13.1 sets out the functional group and a worked example for each). Secondary and tertiary amines are further split by whether the groups attached to nitrogen are identical or not: if all the alkyl or aryl groups on nitrogen are the same, the amine is called simple or symmetrical; if they differ, it is called mixed or unsymmetrical. The second, independent axis is aliphatic versus aromatic, based on the nature of the groups attached to the nitrogen atom -- an aliphatic amine has only alkyl groups on nitrogen, an aromatic amine has at least one aryl group directly on nitrogen. It is worth being careful with this classification, because it works differently from how alkyl halides or alcohols are classified: those are classed 1 degree/2 degree/3 degree by the nature of the CARBON atom bearing the functional group, whereas an amine is classed by how many alkyl/aryl groups sit directly on the NITROGEN atom. This is why isopropylamine, (CH3)2CH-NH2, is a PRIMARY amine (only one carbon group is attached to nitrogen) eve …