http://www.ck12.org Chapter 25. Organic Chemistry
chain. Like alcohols, amines are often referred to as primary, secondary, or tertiary. However, in the case of amines,
this classification tells you how many alkyl chains are attached to the nitrogen atom. The nitrogen atom of a primary
amine is bonded to two hydrogen atoms and one carbon, the nitrogen atom of a secondary amine is bonded to one
hydrogen and two carbons, and the nitrogen atom of a tertiary amine is bonded to three carbon atoms. Recall that
alcohols are labeled as primary, secondary, or tertiary, based on how many alkyl chains are attached to the carbon
that bears the hydroxyl group.
FIGURE 25.21
Although there are IUPAC rules for naming amines, many simple amines are generally referred to by a naming
system that is more closely analogous to the way that ethers are named. This common system for naming amines is
shown below along with several examples.
- Name the alkyl groups that are attached to the nitrogen atom of the amine. If there is more than one different
alkyl group, put them in alphabetical order. If there are two or three of the same alkyl group, use thedi−or
tri−prefix. - Follow the alkyl group name with the suffix –amine, with no spaces.
Properties of Amines
Amines are weak bases due to the presence of a lone pair of electrons on the nitrogen atom. This lone pair can attract
the hydrogen atom from a water molecule, causing the bond between it and the oxygen atom to break. The resultant
products are the conjugate acid of the amine and the hydroxide ion.
Amines are capable of hydrogen bonding, though their boiling points are generally a bit lower than the corresponding
alcohol. Methylamine and ethylamine are gases at room temperature, while larger amines are liquids. As with other