Chemistry of Amines
1. Nomenclature and Structure of Amines
In the IUPAC system of nomenclature, functional groups are normally designated in one of two ways. The presence of the function may be indicated by a characteristic suffix and a location number. This is common for the carbon-carbon double and triple bonds which have the respective suffixesene andyn e. Halogens, on the other hand, do not have a suffix and are named as substituents, for example: (CH3)2C=CHCHClCH3 is 4-chloro-2-methyl-2-pentene. If you are uncertain about the IUPAC rules for nomenclature you should
review them now.
Amines are derivatives of ammonia in which one or more of the hydrogens has been replaced by an alkyl or aryl group. The nomenclature of amines is complicated by the fact that several different nomenclature systems exist, and there is no clear preference for one over the others. Furthermore, the terms primary (1), secondary (2) & tertiary (3) are used to classify amines in a completely different manner than they were used for alcohols or alkyl halides. When applied to amines these terms refer to the number of
alkyl (or aryl) substituents bonded to the nitrogen atom, whereas in other cases they refer to the
nature of an alkyl group. The four compounds shown in the top row of the following diagram are all C4H11N
isomers. The first two are classified as 1-amines, since only one alkyl group is bonded to the nitrogen;
however, the alkyl group is primary in the first example and tertiary in the second. The third and fourth
compounds in the row are 2 and 3-amines respectively. A nitrogen bonded to four alkyl groups will
necessarily be positively charged, and is called a 4-ammonium cation. For example, (CH3)4N(+) Br() is
tetramethylammonium bromide.
The IUPAC names are listed first and colored blue. This system names amine functions as substituents on
the largest alkyl group. The simple -NH2 substituent found in 1-amines is called an amino group. For 2
and 3-amines a compound prefix (e.g. dimethylamino in the fourth example) includes the names of all but
the root alkyl group.
The Chemical Abstract Service has adopted a nomenclature system in which the suffix-amine is attached |
