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11.15: Amines

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     For many people, sleeping problems have to do with an amine that the brain makes called melatonin. This compound affects the sleep-wake cycle and is affected by sunlight. During the winter, the daily cycle of melatonin production may be affected by less sunlight hours. If this cycle is changed, the person may have trouble sleeping. Melatonin supplements are available in pharmacies and health food stores, and may be of help for those with sleeping problems.


    An amine is an organic compound that can be considered to be a derivative of ammonia \(\left( \ce{NH_3} \right)\). The general structure of an amine can be abbreviated as \(\ce{R-NH_2}\), where \(\ce{R}\) is a carbon chain. However, similar to alcohols, amines can be primary, secondary, or tertiary.

    Primary, secondary, and tertiary amines

    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. The nitrogen atom of a tertiary amine is bonded to three carbon atoms. Amines are typically named by a common system, rather than by IUPAC guidelines. The common system for naming amines, along with several examples, is shown below.

    1. 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 the di- or tri- prefix.
    2. Follow the alkyl group name with the suffix -amine, with no spaces.

    Nomenclature of primary, secondary, and tertiary amines

    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.

    Reaction where an amine acts as a base

    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 organic compounds that form hydrogen bonds, water solubility is reflected in the length of the carbon chains. Smaller amines are soluble, while larger ones are less soluble.

    Amines generally have rather pungent or noxious odors. Ammonia can be considered the simplest amine and has a very distinctive odor. Methylamine has an unpleasant odor associated with dead fish. Amines are often formed biologically during the breakdown of proteins in animal cells, and so many have the smell of death and decay. Putrescine and cadaverine are two such amines and are aptly named for their foul odors. The toxins which many animals use as a form of defense are frequently amines. Amines are used industrially as dyes and in many drugs.


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