Aniline

Aniline, phenylamine or aminobenzene ({{carbon}}{{sub|6}}{{hydrogen}}{{sub|5}}{{nitrogen}}{{hydrogen}}{{sub|2}}) is an organic chemical compound which is a primary aromatic amine consisting of a benzene ring and an amino group. The chemical structure of aniline is shown at the right.

Properties

Aniline is oily and, although colourless, it can be slowly oxidized and resinified in air to form impurities which can give it a red-brown tint. Its boiling point is 184 °C and its melting point is -6 °C. It is a liquid at room temperature.

Related Topics:
Boiling point - °C - Melting point

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Like most volatile amines, it possesses a somewhat unpleasant odour of rotten fish, and also has a burning aromatic taste; it is a highly acrid poison. It ignites readily, burning with a large smoky flame.

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Chemically, aniline is a weak base. Aromatic amines such as aniline are generally much weaker bases than aliphatic amines. Aniline reacts with strong acids to form salts containing the anilinium ion (C6H5-NH3+), and reacts with acyl halides (such as acetyl chloride, CH3COCl) to form amides. The amides formed from aniline are sometimes called anilides, for example CH3-CO-NH-C6H5 is acetanilide.

Related Topics:
Base - Aliphatic - Acyl halide - Acetyl chloride - Amide

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The sulphate forms beautiful white plates. Although aniline is but feebly basic, it precipitates zinc, aluminium and ferric salts, and on warming expels ammonia from its salts. Aniline combines directly with alkyl iodides to form secondary and tertiary amines; boiled with carbon disulphide it gives sulphocarbanilide (diphenyl thio-urea), CS(NHC6H5)2, which may be decomposed into phenyl mustard-oil, C6H5CNS, and triphenyl guanidine, C6H5N: C(NHC6H5)2. Sulphuric acid at 180° gives sulphanilic acid, NH2.C6H4.SO3H. Anilides, compounds in which the amino group is substituted by an acid radical, are prepared by heating aniline with certain acids; antifebrin or acetanilide is thus obtained from acetic acid and aniline. The oxidation of aniline has been carefully investigated. In alkaline solution azobenzene results, while arsenic acid produces the violet-colouring matter violaniline. Chromic acid converts it into quinone, while chlorates, in the presence of certain metallic salts (especially of vanadium), give aniline black. Hydrochloric acid and potassium chlorate give chloranil. Potassium permanganate in neutral solution oxidizes it to nitrobenzene, in alkaline solution to azobenzene, ammonia and oxalic acid, in acid solution to aniline black. Hypochlorous acid gives para-amino phenol and para-amino diphenylamine.

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Like phenols, aniline derivatives are highly reactive in electrophilic substitution reactions. For example, sulfonation of aniline produces sulfanilic acid, which can be converted to sulfanilamide. Sulfanilamide is one of the sulfa drugs which were widely used as antibacterials in the early 20th century.

Related Topics:
Phenols - Electrophilic substitution - Sulfanilamide - Sulfa drug - Antibacterial - 20th century

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Aniline and its ring-substituted derivatives react with nitrous acid to form diazonium salts. Through these, the -NH{{sub|2}} group of aniline can be conveniently converted to -OH, -CN, or a halide.

Related Topics:
Nitrous acid - Diazonium salt - Halide

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