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Jai Ganesh

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Aniline

Aniline

Gist

Aniline is a colourless to brown, oily liquid which darkens on exposure to air and light. It has a characteristic amine odour (detectable at 0.6 to 10 ppm ) and burning taste. Hygroscopic. Moderately soluble in water.

Aniline, also known as aminobenzene or phenylamine, has 6 carbon (C) atoms, 7 hydrogen (H) atoms, and 1 nitrogen (N) atom in its chemical formula of C6H7N or C6H5NH2. Because aniline has an amino group in its structure, it is also an amine, hence it is classified as an aromatic amine.

Summary:

Aniline (from Portuguese anil '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

Description

Aniline is used in rubber accelerators and anti-oxidants, dyes and intermediates, photographic chemicals, as isocyanates for urethane foams, in pharmaceuticals, explosives, petroleum refining; and in production of diphenylamine, phenolics, herbicides and fungicides. Aniline is also used in the manufacture of polyurethanes, rubber processing chemicals, pesticides, fibres, dyes and pigments, photographic chemicals, and pharmaceuticals.

Substance details

Substance name: Aniline (benzenamine)

CASR number: 62-53-3

Molecular formula: C6H7N

Synonyms: benzamine; aniline oil, phenylamine; aminobenzene; aniline oil; phenylamine; aminophen; kyanol; benzidam; blue oil; C.I. 76000; C.I. oxidation base 1; cyanol; krystallin; anyvim; arylamine

Physical properties

Aniline is a colourless to brown, oily liquid which darkens on exposure to air and light. It has a characteristic amine odour (detectable at 0.6 to 10 ppm ) and burning taste. Hygroscopic. Moderately soluble in water. Aniline is miscible with alcohol, benzene, chloroform, carbon tetrachloride, acetone, and most organic solvents.

Melting Point: -6.2°C

Boiling Point: 184°C

Specific Gravity: 1.0217

Vapour Density: 3.22

1 ppm = 3.8 mg/m^3
Formula weight 93.128

Chemical properties

Combustible. Darkens on exposure to air and light. The substance decomposes on heating at temperatures above 190°C, or on burning producing toxic and corrosive fumes (ammonia, nitrogen oxides, and carbon monoxide) and flammable vapours. The substance is a weak base. Reacts vigorously with strong oxidants, acids, acetic anhydride, chloromelamine monomers, beta-propiolactone, and epichlorohydrin causing fire and explosion hazard. Reacts with metals such as sodium, potassium, and calcium, producing flammable hydrogen gas. Attacks copper and its alloys.

Description

Short-term exposure to the substance irritates the eyes, and may cause effects on the blood: methaemoglobinaemia, resulting in cyanosis, brain damage and kidney failure. It is potentially lethal to humans.

Long-term or repeated exposure may have effects on the liver, kidneys, blood and spleen: methemoglobanaemia (see short-term exposure). Aniline (benzenamine) is a probable carcinogen.

It does not remain in the body due to its breakdown and removal. Aniline is a possible reproductive hazard.

Entering the body

The substance can be absorbed into the body by inhalation of the vapour, through the skin and by ingestion.

Exposure

Aniline can be formed from the breakdown of certain pollutants found in outdoor air, from the burning of plastics, or from burning tobacco. Airborne exposure to aniline may occur from breathing contaminated air, from smoking tobacco or proximity to someone who is smoking, or from being near industrial sources that use large quantities of aniline.

Occupational exposure to aniline could occur in industries that use aniline to make other chemicals.

Small amounts of aniline may be found in some foods, such as corn, grains, rhubarb, apples, beans, and rapeseed cake (animal feed). Aniline has also been found as a volatile component of black tea. Aniline has been detected in drinking water and has also been found in surface water.

Description

This substance may be hazardous to the environment; with special attention given to fish, crustaceans, and birds. Tests by the aniline industry show that aniline is highly toxic to aquatic life.

Aniline causes germination decrease, stunting, and size decreases (among other effects) on numerous agricultural crops.

Aniline acts to reduce the formation of photochemical smog.

Aniline is unlikely to exist in terrestrial environments in sufficient concentrations to cause serious acute or chronic effects to terrestrial organisms.

Entering the environment

Aniline in solution adsorbs strongly to colloidal organic matter, which effectively increases its solubility and movement into ground water. It is also moderately adsorbed to organic material in the soil. It will slowly volatilise from soil and surface water (vapour pressure 0.67 mm Hg @ 25°C) and is subject to biodegradation. Although rapidly degraded in the atmosphere, aniline can be deposited in the soil by wet and dry deposition, and by adsorption on aerosol particles.

Where it ends up

Air: Aniline degrades in the atmosphere primarily by reaction with photochemically produced hydroxyl radicals. The estimated half-life for aniline is 2 hours. The reaction products include nitrosamines, nitrobenzene, formic acid, nitrophenols, phenol, nitrosobenzene, and benzidine.

Soil: A number of microorganisms in soil can use aniline as a sole carbon and nitrogen source. Degradation of 44.2% of the incubated aniline to CO2in 10 days and 12% in 20 days, respectively, by different isolated soil microorganisms has been demonstrated in the laboratory. Aniline bound to humic materials in the soil is subject to oxidation. Products apparently formed from oxidation include azobenzene, azoxybenzene, phenazine, formanilide, and acetanilide. Photodegradation of aniline on the soil surface is also thought to be an environmentally important removal process. The combination of these processes eventually results in the degradation of aniline to CO2. The half-life for the mineralisation of aniline to CO2 has been estimated at 4 days, utilising a model soil ecosystem. Information from studies done obtained under environmental conditions indicate that the half-life of aniline in the soil is less than one week

Water: Aniline in water is subject to biodegradation, photodegradation, and adsorption to sediment and humic materials. Low pH will increase the removal of aniline by adsorption; however, the adsorption to colloidal particles can extend the persistence of aniline in the aquatic environment. Although subject to oxidation when adsorbed to humic materials, aniline is resistant to hydrolysis. A half-life for aniline of 2.3 days has been reported in an industrial river. The presence of humic acids and various species of algae in the water can increase the photodegradation rates of aniline up to 50 fold.

Biota: The bioconcentration factor in two species of fish has been estimated at less than 1. A bioconcentration factor of 3 has also been calculated for fish. Aniline is not expected to accumulate significantly in aquatic organisms; however, it is absorbed and metabolised by fish.

Industry sources

Effluents from oil shale recovery and oil refiners, and from chemical and coal conversion plants.

Diffuse sources, and industry sources included in diffuse emissions data

Cigarette smoke. Agricultural uses of products containing or made from aniline.

Natural sources

It occurs naturally in some foods (for example, in corn, grains, beans, and tea), and in coal tars.

Consumer products

Aniline is predominantly used as a chemical intermediate for the dye, agricultural, polymer, and rubber industries. As such, there are few products directly containing aniline. Nevertheless, aniline is used as a solvent, and has been used as an antiknock compound for petrol.

Additional Information

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.

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