AMINE

any member of a family of nitrogen-containing organic compounds that is derived, either in principle or in practice, from ammonia (NH3). Amines are classified as primary, secondary, or tertiary depending on whether one, two, or three of the hydrogen atoms of ammonia have been replaced by organic groups. Diamines, triamines, and polyamines contain two, three, or more nitrogen groupings of the aforementioned types. Amines are alkaline, although the intensity of this property varies. Naturally occurring amines include the alkaloids, which are present in certain plants; the catecholamine neurotransmitters (i.e., dopamine, norepinephrine, and epinephrine); and a local chemical mediator, histamine, that occurs in most animal tissues. Aniline, ethanolamines, and several other amines are major industrial commodities used in making rubber, dyes, pharmaceuticals, and synthetic resins and fibres and in a host of other applications. Most of the numerous methods for the preparation of amines may be broadly divided into two groups: (1) chemical reduction (replacement of oxygen with hydrogen atoms in the molecule) of members of several other classes of organic nitrogen compounds and (2) reactions of ammonia or amines with organic compounds. Amines form salts with acids; with many organic acids or acid anhydrides, primary and secondary amines undergo further reaction to form amides.