Amide A derivative of a carboxylic acid with general formula RCONH2, where R is hydrogen or an alkyl or aryl radical. Amides are divided into subclasses, depending on the number of substituents on nitrogen. The simple, or primary, amides are considered to be derivatives formed by replacement of the carboxylic hydroxyl group by the amino group, NH2. They are named by dropping the “-ic acid” or “-oic acid” from the name of the parent carboxylic acid and replacing it with the suffix “amide.” In the secondary and tertiary amides, one or both hydrogens are replaced by other groups. The presence of such groups is designated by the prefix capital N (for nitrogen).

Except for formamide, all simple amides are relatively low-melting solids, stable, and weakly acidic. They are strongly associated through hydrogen bonding, and hence soluble in hydroxylic solvents, such as water and alcohol. Because of ease of formation and sharp melting points, amides are frequently used for the identification of organic acids and, conversely, for the identification of amines.

Commercial preparation of amides involves thermal dehydration of ammonium salts of carboxylic acids. Thus, slow pyrolysis of ammonium acetate forms water and ac­etamide. N, N-dimethylacetamide may be similarly prepared from dimethylammonium acetate.

Amides are important chemical intermediates since they can be hydrolyzed to acids, dehydrated to nitrites, and degraded to amines containing one less carbon atom by the Hofmann reaction. In pharmacology, acetophenetidin is a popular analgesic. However, the most important commercial application of amides is in the preparation of polyamide resins, also called nylons.

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عن Akram Amir El Ali

استاذ الكيمياء التحليلية ومصمم غرافيك

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