Math Is Fun Forum

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 51,694

Aniline

Aniline

Gist

Aniline, or benzenamine (C6H5NH2), is the simplest aromatic amine, an industrially important organic compound used to make dyes, rubber, plastics, and other chemicals. It is a colorless to brown, oily liquid that darkens on exposure to air and light and has a characteristic odor. Aniline is a weak base, easily absorbed by the skin, and is a combustible liquid that can form flammable vapor/air mixtures and produce toxic fumes when heated or burned.

Aniline was first obtained in 1826 by the destructive distillation of indigo. Its name is taken from the specific name of the indigo-yielding plant Indigofera anil (Indigofera suffruticosa); its chemical formula is C6H5NH2.

Aniline is a chemical intermediate used to make a wide range of products, including dyes, pharmaceuticals (like paracetamol and Tylenol), polyurethane plastics, and rubber products like tires. It is also used in the agricultural industry to produce pesticides and fungicides.

Summary

Aniline (From Portuguese: anil, meaning 'indigo shrub', and -ine indicating a derived substance) is an organic compound with the formula C6H5NH2. Consisting of a phenyl group (−C6H5) attached to an amino group (−NH2), aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starting material for fine chemical synthesis. Its main use is in the manufacture of precursors to polyurethane, dyes, and other industrial chemicals. Like most volatile amines, it has the odor of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. It is toxic to humans.

Relative to benzene, aniline is "electron-rich". It thus participates more rapidly in electrophilic aromatic substitution reactions. Likewise, it is also prone to oxidation: while freshly purified aniline is an almost colorless oil, exposure to air results in gradual darkening to yellow or red, due to the formation of strongly colored, oxidized impurities. Aniline can be diazotized to give a diazonium salt, which can then undergo various nucleophilic substitution reactions.

Like other amines, aniline is both a base (pKaH = 4.6) and a nucleophile, although less so than structurally similar aliphatic amines.

Because an early source of the benzene from which they are derived was coal tar, aniline dyes are also called coal tar dyes.

Details

Aniline is an organic base used to make dyes, drugs, explosives, plastics, and photographic and rubber chemicals.

Aniline was first obtained in 1826 by the destructive distillation of indigo. Its name is taken from the specific name of the indigo-yielding plant Indigofera anil (Indigofera suffruticosa); its chemical formula is C6H5NH2.

Aniline is prepared commercially by the catalytic hydrogenation of nitrobenzene or by the action of ammonia on chlorobenzene. The reduction of nitrobenzene can also be carried out with iron borings in aqueous acid.

A primary aromatic amine, aniline is a weak base and forms salts with mineral acids. In acidic solution, nitrous acid converts aniline into a diazonium salt that is an intermediate in the preparation of a great number of dyes and other organic compounds of commercial interest. When aniline is heated with organic acids, it gives amides, called anilides, such as acetanilide from aniline and acetic acid. Monomethylaniline and dimethylaniline can be prepared from aniline and methyl alcohol. Catalytic reduction of aniline yields cyclohexylamine. Various oxidizing agents convert aniline to quinone, azobenzene, nitrosobenzene, p-aminophenol, and the phenazine dye aniline black.

Pure aniline is a highly poisonous, oily, colourless substance with a pleasant odour.

Additional Information

Aniline is the simplest member of the primary aromatic amines, in which one or more hydrogen atoms of the benzene ring are replaced by amino (-NH2) group.

Derivatives of aniline include a wide variety of different substances. Some of these (like benzidine and MOCA) are composed of two combined aromatic rings.

Many aromatic amines may cause methemoglobinemia in humans. Aniline and many of its derivatives are known or suspected human carcinogens. Several aniline derivatives can also cause skin sensitization. Classical members of this family are bladder carcinogens 2-naphtylamine and benzidine, both of which have been restricted in the European Union (EU) implying that there is no exposure to these compounds.

A large number of substances in the aniline group are on the market in the EU. Several aniline derivatives can be found also from the list of substances restricted under REACH. Aniline compounds are also formed as degradation products from azo-colourants, pharmaceuticals and from aromatic isocyanates used for polyurethane polymers, lacquers, foams and adhesives.

When looking at those aniline substances that are produced or imported in the EU at amounts above 1,000 tonnes per year (tpa) according to the European Chemical Agency’s (ECHA) registration database and that have significant health hazards, (other than only irritation/corrosion).

---

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.