The Foundations of Chemistry

AMINES

The aminesare derivatives of ammonia in which one or more hydrogen atoms have been

replaced by alkyl or aryl groups. Many low-molecular-weight amines are gases or low-

boiling liquids (Table 27-10). Amines are basic compounds (Table 18-6, Section 28-4).

The aliphatic amines of low molecular weight are soluble in water. Aliphatic diamines of

fairly high molecular weight are soluble in water because each molecule contains two

highly polar XNH 2 groups that form hydrogen bonds with water.

The odors of amines are quite unpleasant; many of the malodorous compounds that

are released as fish decay are low-molecular-weight amines. Amines of high molecular

weight are nonvolatile, so they have little odor. One of the materials used to manufacture

nylon, hexamethylenediamine, is an aliphatic amine. Many aromatic amines are used to

prepare organic dyes that are widely used in industrial societies. Amines are also used to

produce many medicinal products, including local anesthetics and sulfa drugs.

Amines are widely distributed in nature in the form of amino acids and proteins, which

are found in all higher animal forms, and in alkaloids, which are found in most plants.

27-12

CH 3 CH C

CH 2

(CH 2 ) 12

muscone

(musk deer, used

in perfumes)

testosterone

(male sex hormone)

camphor

O

O

H 3 C

OH

O

H 3 C

H 3 C

CH 3

CH 3

CH

benzaldehyde

(almonds)

cinnamaldehyde

(cinnamon)

vanillin

(vanilla)

O

CH CH CH

O

HO

OCH 3

CH

O

Ammonia acts as a Lewis base because
there is one unshared pair of electrons
on the N atom (Section 10-10).

1074 CHAPTER 27: Organic Chemistry I: Formulas, Names, and Properties

TABLE 27-10 Boiling Points of Ammonia and Some Amines

Name Formula Boiling Point (°C)

ammonia NH 3 33.4

methylamine CH 3 NH 2 6.5

dimethylamine (CH 3 ) 2 NH 7.4

trimethylamine (CH 3 ) 3 N 3.5

ethylamine CH 3 CH 2 NH 2 16.6

aniline C 6 H 5 NH 2 184

ethylenediamine H 2 NCH 2 CH 2 NH 2 116.5

pyridine C 5 H 5 N 115.3

pyrrole C 4 H 5 N 129.8