Aniline Chemical Properties
- Melting point:
- -6.2 °C
- Boiling point:
- 184 °C(lit.)
- 1.022 g/mL at 25 °C(lit.)
- vapor density
- 3.22 (185 °C, vs air)
- vapor pressure
- 0.7 mm Hg ( 25 °C)
- refractive index
- Flash point:
- 76 °C
- storage temp.
- water: soluble
- 4.63(at 25℃)
- APHA: ≤250
- Specific Gravity
- Relative polarity
- Sweet, amine-like odor detectable at 0.6 to 10 ppm
- 8.8 (36g/l, H2O, 20℃)
- PH Range
- explosive limit
- Water Solubility
- 36 g/L (20 ºC)
- Henry's Law Constant
- 1.91 at 25 °C (thermodynamic method-GC/UV spectrophotometry, Altschuh et al., 1999)
- Exposure limits
- TLV-TWA skin 2 ppm (～8 mg/m3) (ACGIH), 5 ppm (～19 mg/m3) (MSHA, OSHA, and NIOSH); IDLH 100 ppm (NIOSH).
- Stable. Incompatible with oxidizing agents, bases, acids, iron and iron salts, zinc, aluminium. Light sensitive. Combustible.
- CAS DataBase Reference
- 62-53-3(CAS DataBase Reference)
- NIST Chemistry Reference
- EPA Substance Registry System
- Aniline (62-53-3)
- Hazard Codes
- Risk Statements
- Safety Statements
- UN 1547 6.1/PG 2
- WGK Germany
- Autoignition Temperature
- 615 °C
- HS Code
- 2921 41 00
- Hazardous Substances Data
- 62-53-3(Hazardous Substances Data)
- LD50 orally in rats: 0.44 g/kg (Jacobson)
Aniline Usage And Synthesis
Aniline is the simplest primary aromatic amine and a compound formed by the substitution of a hydrogen atom in the benzene molecule with an amino group. It is colorless oil like flammable liquid with strong odor. When heated to 370 C, it is slightly soluble in water and soluble in ethanol, ether, chloroform and other organic solvents. It becomes brown in the air or under the sun. It can be distilled by steam. A small amount of zinc powder is added to prevent oxidation when it is distilled. The purified aniline can be added 10 ~ 15ppm NaBH4 to prevent oxidation deterioration. The solution of aniline is alkaline.
It is easy to produce salt when it reacts with acid. The hydrogen atoms on its amino groups can be substituted by alkyl or acyl groups to produce second or third grade aniline and acyl aniline. When substitution reaction occurs, the products of ortho and para substituted products are mainly produced. It reacts with nitrite to form diazonium salts, which can be used to produce a series of benzene derivatives and azo compounds.
Aniline is predominantly used as a chemical intermediate for dyes, drugs, explosives, plastics, and photographic and rubber chemicals. Many chemicals can be made from Aniline, including:
- Isocyanaates for the urethane industry
- Antioxidants, activators, accelerators, and other chemicals for the rubber industry
- Indigo, acetoacetanilide, and other dyes and pigments for a variety of applications
- Diphenylamine for the rubber, petroleum, plastics, agricultural, explosives, and chemical industries
- Various fungacides and herbicides for the agricultural industry
- Pharmaceutical, organic chemical, and other products
Many industrial feedstocks including N-alkylaniline, alkylaniline, o-nitroaniline, O-benzyl two amine, phenyl hydrazine, cyclohexanamine, etc is derived from Aniline. It can be used as the intermediates of the fungicide sodium p-aminobenzenesulfonate, SSEED, methyl sterilamine, sterilized amine, carbendazim, pyrazinyl, Benzalin, insecticide, pyrazino, pyrazino, pyrazino, pyrazinophos, herbicide methamidine, acetochlor, butachlor, cyclohexanone, imidazolinic acid etc.
A primary aromatic amine, aniline is a weak base and forms salts with mineral acids such as aniline hydrochloride. PKb = 9.30, 0.2mol aqueous solution PH value 8.1. 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. Amino groups can undergo acylation, halogenation, alkylation and diazotization, and the presence of amino groups makes it nucleophiles capable of many nucleophilic reactions, and at the same time activates the electrophilic substitution on aromatic rings.
Aniline was first obtained in 1826 by the destructive distillation of indigo. It is named because of the specific indigo-yielding plant “Indigofera anil” (Indigofera suffruticosa); In 1857, W.H.Jr. Perkin made aniline from reduction of nitrobenzene with iron filings using hydrochloric acid as catalyst which is still being used. At present, the methods of aniline production include catalytic vapor phase reduction of nitrobenzene with hydrogen, catalytic reaction of chlorobenzene and ammonolysis of phenol (Japan).
Before 1960s, aniline production was based on coal tar benzene, and now petroleum benzene has been used. At the end of 1990s, the world's aniline production capacity was above 2.5 million t. 50% of the aniline is used in the production of dye intermediates. About 25% aniline is used to produce isocyanate and its copolymers. The remaining (25%) is used for pesticides, gasoline antiknock agents, and photographic materials etc.
Reduction of nitrobenzene with hydrogen
Aniline is currently obtained by catalytic hydrogenation of nitrobenzene. The catalyst usually used is Cu-SiO2, which has good selectivity and can successfully reduce nitrobenzene to aniline. It is not easy to produce hydrogenation on benzene core. The reaction is carried out in a fluidized bed reactor. After purification, the hydrogen is heated by the heater to 350~400℃.
And then it is ushered in the evaporator, while nitrobenzene enters the evaporator from the upper trough, and contacts with the hot hydrogen to be gasified and overheat to 180~223 ℃.
The mixed gas enters from the bottom of the fluidized bed and contacts with the copper catalyst loaded on the silica gel in the fluidized bed. The generated crude aniline and water vapor are discharged from the top of the bed. Crude benzylamine is cooled and separated by a condenser, and then finished aniline is rectified.
The toxicity of Aniline is LD50500mg/kg (dog oral administration), and is a common pollutant in the environment. Aniline has strong toxicity to blood and nerves. It can be absorbed by skin or by respiratory tract to cause toxicity.
The acute (short-term) and chronic (long-term) effects of aniline in humans consist mainly of effects on the lung, such as upper respiratory tract irritation and congestion. Chronic exposure may also result in effects on the blood. Human cancer data are insufficient to conclude that aniline is a cause of bladder tumors while animal studies indicate that aniline causes tumors of the spleen. EPA has classified aniline as a Group B2, probable human carcinogen.
Evidence reported by the National Institute for Occupational Safety and Health (NIOSH) clearly associates the occupational exposure to o-toluidine and aniline with an increased risk of bladder cancer among workers. The risk of bladder cancer is greatest among workers with possible and definite exposures to o-toluidine and aniline, and the risk increases with the duration of exposure.
Aniline,C6H5NH2, is slightly soluble in water,miscible in alcohol and ether,and turns yellow to brown in air. Aniline may be made(1) by the reduction, with iron or tin in HCI, of nitrobenzene, and(2) by the amination of chlorobenzene by heating with ammonia to a high temperature corresponding to a pressure of over 200 atmospheres in the presence of a catalyst(a mixture of cuprous chlorideandoxide).Aniline is the end point of reduction of most mononitrogen substituted benzene nuclei,as nitro benzene beta-phenyl hydroxylamine, azoxybenzene, azobenzene, hydrazobenzene. Aniline is detected by the violet coloration produced by a small amountof sodium hypochlorite. Aniline is used as a solvent, in the preparation of compound in the manufacture of dyes and their intermediates, and in the manufacture of medicinal chemicals.
Aniline was first isolated from the destructive distillation of indigo in 1826 by Otto Unverdorben. Aniline is oily and, although colorless, it slowly oxidizes and turns into a kind of resin in air, giving the sample a red-brown tint. At room temperature, aniline, the simplest aromatic amine, is a clear to slightly yellow, oily liquid that darkens to a brown color on exposure to air. Like most volatile amines, it possesses the somewhat unpleasant odor of rotten fi sh and also has a burning aromatic taste. It has a low vapor pressure at room temperature and ignites readily, burning with a smoky flame. It does not readily evaporate at room temperature. Aniline is slightly soluble in water and mixes readily with most organic solvents. It is synthesized by catalytic hydrogenation of nitrobenzene or by ammonolysis of phenol. Aniline is incompatible with strong acids, strong oxidizers, albumin, and solutions of iron, zinc, aluminum, toluene diisocyanate, and alkalis. It ignites spontaneously in the presence of red fuming nitric acid, and with sodium. Originally, the great commercial value of aniline was due to the readiness with which it yields, directly or indirectly, valuable dyestuffs. Currently, the largest market for aniline is in the preparation of methylene diphenyl diisocyanate (MDI), some 85% of aniline serving this market. In fact, in industry, aniline is an initiator or intermediary in the synthesis of aniline being used as a precursor to more complex chemicals. It is the starting material for many dyestuffs, known as aniline dyes. Its main application is in the manufacture of polyurethane foam, and a wide variety of products, such as MDI, agricultural chemicals, synthetic dyes, antioxidants, stabilizers for the rubber industry, varnishes, explosives, analgesics, and hydroquinone for photographic developing, and as an octane booster in gasoline. Aniline has also been detected in tobacco smoke and exposures to aniline have been reported among workers in related industrial workplaces, hazardous waste sites, and the general population through food and drinking water.
Colorless, oily liquid with a faint ammonia-like odor and burning taste. Gradually becomes yellow to reddish-brown on exposure to air or light. The lower and upper odor thresholds are 2 and 128 ppm, respectively (quoted, Keith and Walters, 1992). An odor threshold of 1.0 ppmv was reported by Leonardos et al. (1969).
Aniline is used in the manufacture of dyes,pharmaceuticals, varnishes, resins, photo graphic chemicals, perfumes, shoe blacks,herbicides, and fungicides. It is also usedin vulcanizing rubber and as a solvent. Itoccurs in coal tar and is produced from thedry distillation of indigo. It is also producedfrom the biodegradation of many pesticides.Aniline is a metabolite of many toxic com pounds, such as nitrobenzene, phenacetin,and phenylhydroxylamine.
Rubber accelerators and antioxidants, dyes and intermediates, photographic chemicals (hydro- quinone), isocyanates for urethane foams, pharma- ceuticals, explosives, petroleum refining, dipheny- lamine, phenolics, herbicides, fungicides.
A thin, colorless oil prepared by reducing benzene with iron filings in the presence of hydrochloric or acetic acid and then separating the aniline formed by distillation. It is slightly soluble in water but dissolves easily in alcohol, ether, and benzene. Aniline is the base for many dyes used to increase the sensitivity of emulsions.
ChEBI: A primary arylamine in which an amino functional group is substituted for one of the benzene hydrogens.
Aniline was obtained in 1826 by Unverdorben from distillation of indigo and was given the name aniline in 1841 by Fritzsche (Windholz et al 1983). The chemical was manufactured in the U. S. by the Bechamp reaction involving reduction of nitrobenzene in the presence of either copper/silica or hydrochloric acid/ferrous chloride catalysts; but in 1966, amination of chlorobenzene with ammonia was introduced (IARC 1982; Northcott 1978). Currently, aniline is produced in the U.S., several European countries and Japan by the catalytic hydrogenation of nitrobenzene in either the vapor phase or solvent system. This chemical is also produced by reacting phenol with ammonia (HSDB 1989). Production in 1982 amounted to 331,000 tons (HSDB 1989).
A yellowish to brownish oily liquid with a musty fishy odor. Melting point -6°C; boiling point 184°C; flash point 158°F. Denser than water (8.5 lb / gal) and slightly soluble in water. Vapors heavier than air. Toxic by skin absorption and inhalation. Produces toxic oxides of nitrogen during combustion. Used to manufacture other chemicals, especially dyes, photographic chemicals, agricultural chemicals and others.
Air & Water Reactions
Darkens on exposure to air and light. Polymerizes slowly to a resinous mass on exposure to air and light. Slightly soluble in water.
Aniline is a heat sensitive base. Combines with acids to form salts. Dissolves alkali metals or alkaline earth metals with evolution of hydrogen. Incompatible with albumin, solutions of iron, zinc and aluminum, and acids. Couples readily with phenols and aromatic amines. Easily acylated and alkylated. Corrosive to copper and copper alloys. Can react vigorously with oxidizing materials (including perchloric acid, fuming nitric acid, sodium peroxide and ozone). Reacts violently with BCl3. Mixtures with toluene diisocyanate may ignite. Undergoes explosive reactions with benzenediazonium-2-carboxylate, dibenzoyl peroxide, fluorine nitrate, nitrosyl perchlorate, peroxodisulfuric acid and tetranitromethane. Violent reactions may occur with peroxyformic acid, diisopropyl peroxydicarbonate, fluorine, trichloronitromethane (293° F), acetic anhydride, chlorosulfonic acid, hexachloromelamine, (HNO3 + N2O4 + H2SO4), (nitrobenzene + glycerin), oleum, (HCHO + HClO4), perchromates, K2O2, beta-propiolactone, AgClO4, Na2O2, H2SO4, trichloromelamine, acids, FO3Cl, diisopropyl peroxy-dicarbonate, n-haloimides and trichloronitromethane. Ignites on contact with sodium peroxide + water. Forms heat or shock sensitive explosive mixtures with anilinium chloride (detonates at 464° F/7.6 bar), nitromethane, hydrogen peroxide, 1-chloro-2,3-epoxypropane and peroxomonosulfuric acid. Reacts with perchloryl fluoride form explosive products. .
An allergen. Toxic if absorbed through the skin. Combustible. Skin irritant. Questionable car- cinogen.
Aniline is a moderate skin irritant, a moderate to severe eye irritant, and a skin sensitizer in animals. Aniline is moderately toxic via inhalation and ingestion. Symptoms of exposure (which may be delayed up to 4 hours) include headache, weakness, dizziness, nausea, difficulty breathing, and unconsciousness. Exposure to aniline results in the formation of methemoglobin and can thus interfere with the ability of the blood to transport oxygen. Effects from exposure at levels near the lethal dose include hypoactivity, tremors, convulsions, liver and kidney effects, and cyanosis. Aniline has not been found to be a carcinogen or reproductive toxin in humans. Some tests in rats demonstrate carcinogenic activity. However, other tests in which mice, guinea pigs, and rabbits were treated by various routes of administration gave negative results. Aniline produced developmental toxicity only at maternally toxic dose levels but did not have a selective toxicity for the fetus. It produces genetic damage in animals and in mammalian cell cultures but not in bacterial cell cultures.
Combustion can produce toxic fumes including nitrogen oxides and carbon monoxide. Aniline vapor forms explosive mixtures with air. Aniline is incompatible with strong oxidizers and strong acids and a number of other materials. Avoid heating. Hazardous polymerization may occur. Polymerizes to a resinous mass.
Flammability and Explosibility
Aniline is a combustible liquid (NFPA rating = 2). Smoke from a fire involving aniline may contain toxic nitrogen oxides and aniline vapor. Toxic aniline vapors are given off at high temperatures and form explosive mixtures in air. Carbon dioxide or dry chemical extinguishers should be used to fight aniline fires.
Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Flush with water and rinse with dilute acetic acid; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.
Aniline, the simplest primary aromatic amine, consists of a nitrogen atom with two
attached hydrogen atoms affixed to a benzene ring. This aromatic amine is a
weaker base than the aliphatic amines but aniline does undergo many of the same
reactions in the realm of synthetic chemistry. Aniline is used to prepare agricultural
chemicals, antioxidants, fungicides, herbicides, isocyanates, and other
commercially important chemicals.
Aniline is used as a chemical intermediate to prepare isocyanates for making polyurethanes, antioxidants, and vulcanization accelerators, as well as in the manufacture of agricultural fungicides, herbicides and insecticides and in the preparation of certain dyes.
Suspected carcinogen with experimental neoplastigenic data. A human poison by an unspecified route. Poison experimentally by most routes incluhng inhalation and ingestion. Experimental reproductive effects. A skin and severe eye irritant, and a rmld sensitizer. In the body, aniline causes formation of methemoglobin, resulting in prolonged anoxemia and depression of the central nervous system; less acute exposure causes hemolysis of the red blood cells, followed by stimulation of the bone marrow. The liver may be affected with resulting jaundice. Long-term exposure to a d n e dye manufacture has been associated with malignant bladder growths. A common air contaminant, A combustible liquid when exposed to heat or flame. To fight fire, use alcohol foam, CO2, dry chemical. It can react vigorously with oxidizing materials. When heated to decomposition it emits highly toxic fumes of NOx. Spontaneously explosive reactions occur with benzenediazonium-2-carboxylate, dibenzoyl peroxide, fluorine nitrate, nitrosyl perchlorate, red fuming nitric acid, peroxodisulfuric acid, and tetranitromethane. Violent reactions with boron trichloride, peroxyformic acid, dhsopropyl peroxydicarbonate, fluorine, trichloronitromethane (145℃), acetic anhydride, chlorosulfonic acid, hexachloromelamine, (HNO3 + N2O4 + H2SO4), (nitrobenzene + glycerin), oleum, (HCHO + HClO4), perchromates, K2O2, ppropiolactone, AgClO4, Na2On, H2SO4, trichloromelamine, acids, peroxydisulfuric acid, F03Cl, diisopropyl peroxy-dicarbonate, n-haloimides, and trichloronitromethane. Ignites on contact with sodium peroxide + water. Forms heator shock-sensitive explosive mixtures with anhnium chloride (detonates at 240°C/7.6 bar), nitromethane, hydrogen peroxide, 1 -chloro-2,3- epoxypropane, and peroxomonosulfuric acid. Reactions with perchloryl fluoride, perchloric acid, and ozone form explosive products.
Aniline is widely used as an intermediate in the synthesis of dyestuffs. It is also used in the manufacture of rubber accelerators and antioxidants, pharmaceuticals, marking inks; tetryl, optical whitening agents; photographic developers; resins, varnishes, perfumes, shoe polishes, and many organic chemicals.
The IARC has classified aniline as a Group 3 carcinogen, that is, not classifiable as to its carcinogenicity. However, NIOSH has determined that there is sufficient evidence to recommend that OSHA require labeling this substance a potential occupational carcinogen. This position followed an evaluation of a high-dose feeding study of aniline hydrochloride in F344 rats and B6C3F1 mice (3000 or 6000 ppm and 6000 or 12,000 ppm, respectively). The test was negative in both sexes of mice; however, hemangiosarcomas of the spleen and combined incidence of fibrosarcomas and sarcomas of the spleen were statistically significant in the male rats; the number of female rats having fibrosarcomas of the spleen was also significant.
Detected in distilled water-soluble fractions of regular gasoline (87 octane) and Gasohol
at concentrations of 0.55 and 0.20 mg/L, respectively (Potter, 1996). Aniline was also detected in
82% of 65 gasoline (regular and premium) samples (62 from Switzerland, 3 from Boston, MA). At
25 °C, concentrations ranged from 70 to 16,000 μg/L in gasoline and 20 to 3,800 μg/L in watersoluble
fractions. Average concentrations were 5.8 mg/L in gasoline and 1.4 mg/L in watersoluble
fractions (Schmidt et al., 2002).
Based on laboratory analysis of 7 coal tar samples, aniline concentrations ranged from ND to 13 ppm (EPRI, 1990).
Aniline in the environment may originate from the anaerobic biodegradation of nitrobenzene (Razo-Flores et al., 1999).
Biological. Under anaerobic conditions using a sewage inoculum, 10% of the aniline present
degraded to acetanilide and 2-methylquinoline (Hallas and Alexander, 1983). In a 56-d
experiment, [14C]aniline applied to soil-water suspensions under aerobic and anaerobic conditions
gave 14CO2 yields of 26.5 and 11.9%, respectively (Scheunert et al., 1987). A bacterial culture
isolated from the Oconee River in North Georgia degraded aniline to the intermediate catechol
(Paris and Wolfe, 1987). Aniline was mineralized by a soil inoculum in 4 d (Alexander and
Soil. A reversible equilibrium is quickly established when aniline covalently bonds with humates in soils forming imine linkages. These quinoidal structures may oxidize to give nitrogensubstituted quinoid rings. The average second-order rate constant for this reaction in a pH 7 buffer at 30 °C is 9.47 x 10-5 L/g?h (Parris, 1980). In sterile soil, aniline partially degraded to azobenzene, phenazine, formanilide, and acetanilide and the tentatively identified compounds nitrobenzene and p-benzoquinone (Pillai et al., 1982).
Surface Water. Aniline degraded in pond water containing sewage sludge to catechol, which then degrades to carbon dioxide. Intermediate compounds identified in minor degradative pathways include acetanilide, phenylhydroxylamine, cis,cis-muconic acid, β-ketoadipic acid, levulinic acid, and succinic acid (Lyons et al., 1984).
Photolytic. A carbon dioxide yield of 46.5% was achieved when aniline adsorbed on silica gel was irradiated with light (λ >290 nm) for 17 h (Freitag et al., 1985). Products identified from the gas-phase reaction of ozone with aniline in synthetic air at 23 °C were nitrobenzene, formic acid, hydrogen peroxide, and a nitrated salt having the formula: [C6H5NH3]+NO3 - (Atnagel and Himmelreich, 1976). A second-order rate constant of 6.0 x 10-11 cm3/molecule?sec at 26 °C was reported for the vapor-phase reaction of aniline and OH radicals in air at room temperature (Atkinson, 1985).
Chemical/Physical. Alkali or alkaline earth metals dissolve in aniline with hydrogen evolution and the formation of anilides (Windholz et al., 1983). Laha and Luthy (1990) investigated the redox reaction between aniline and a synthetic manganese dioxide in aqueous suspensions at the pH range 3.7–6.5. They postulated that aniline undergoes oxidation by loss of one electron forming cation radicals. These radicals may undergo head-to-tail, tail-to-tail, and head-to-head couplings forming 4-aminophenylamine, benzidine, and hydrazobenzene, respectively. These compounds were additionally oxidized, in particular, hydrazobenzene to azobenzene at pH 4 (Laha and Luthy, 1990).
Aniline is absorbed from the skin and the gastrointestinal tract (BaranowskaDutkeiwicz 1982). It is excreted primarily in the urine of treated rabbits with only a small fraction (2%) of the administered dose excreted in the feces (Kao et al 1978; Parke 1960) and none in the expired air. Urinary metabolites of aniline include P-aminophenol, O-aminophenol, m-aminophenol, aniline-N-glucuronide, phenylsulfonic acid and acetanilide (Parke, 1960). Aminophenyl- and acetylaminophenyl-mercapturic acids also have been detected in the urine of rats and rabbits (IARC 1982). Excretion of aniline conjugates of P-aminophenol have been observed in human urine (Williams 1959) and urinary excretion of these conjugates has been found to reflect the extent of absorption of aniline vapor through the skin and respiratory tract (Kao et al 1978; Piotrowski 1972). The methemoglobinemia produced in humans by aniline is believed to result from its N-hydroxylation (IARC 1982). Aniline also is a weak inducer of hepatic microsomal enzymes. Subcutaneous injections of 5 mg/kg body weight for 30 days to rats impaired aniline metabolism in vivo but it increased its in vitro metabolism to p-aminophenol (Wisniewska-Knypl and Jablonska 1975; Wisniewska-Knypl et al 1975). Low protein diets decreased hepatic aniline hydroxylation in the rat (Kato et al 1968). Saturated fat increased aniline metabolism by rat liver independent of chemical composition of the fat used (Caster et al 1970). Highest initial concentrations of aniline derived radioactivity were found in blood, liver, kidney, bladder, and gastrointestinal tract of rat, given labelled compound i.v. After 0.5 h and 6 h, radioactivity concentrated in the stomach and jejunum and subsequently absorbed from the intestine indicating the presence of an enterogastric cycle in rats. Aniline was the predominant compound in the gastric contents of treated animals and acetanilide is the major metabolite found in the jejunal contents (Irons et al 1980).
Aniline should be kept stored against physical damage in a cool (but not freezing), dry, well-ventilated location, away from smoking areas and fi re hazard. It should be kept separated from incompatibles and the containers should be bonded and grounded for transfer to avoid static sparks
UN1547 Aniline, Hazard Class: 6.1; Labels: 6.1- Poisonous materials. UN1548 Aniline hydrochloride, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.
Aniline is hygroscopic. It can be dried with KOH or CaH2, and distilled under reduced pressure. Treatment with stannous chloride removes sulfur-containing impurities, reducing the tendency to become coloured by aerial oxidation. It can be crystallised from Et2O at low temperatures. More extensive purifications involve preparation of derivatives, such as the double salt of aniline hydrochloride and cuprous chloride or zinc chloride, or N-acetylaniline (m 114o) which can be recrystallised from water. Redistilled aniline is dropped slowly into a strong aqueous solution ofrecrystallised oxalic acid. Aniline oxalate (m 174-175o) is filtered off, washed several times with water and recrystallised three times from 95% EtOH. Treatment with saturated Na2CO3 solution regenerated aniline which was distilled from the solution, dried and redistilled under reduced pressure [Knowles Ind Eng Chem 12 881 1920]. After refluxing with 10% acetone for 10hours, aniline is acidified with HCl (Congo Red as indicator) and extracted with Et2O until colourless. The hydrochloride is purified by repeated crystallisation before aniline is liberated by addition of alkali, then dried with solid KOH, and distilled. The product is sulfur-free and remains colourless in air [Hantzsch & Freese Chem Ber 27 2529, 2966 1894]. Non-basic materials, including nitro compounds, are removed from aniline in 40% H2SO4 by passing steam through the solution for 1hour. Pellets of KOH are then added to liberate the aniline which is steam distilled, dried with KOH, distilled twice from zinc dust at 20mm, dried with freshly prepared BaO, and finally distilled from BaO in an all-glass apparatus [Few & Smith J Chem Soc 753 1949]. Aniline is absorbed through skin and is TOXIC.[Beilstein 12 IV 223.]
May form explosive mixture with air. Unless inhibited (usually methanol), aniline is readily able to polymerize. Fires and explosions may result from contact with halogens, strong acids; oxidizers, strong base organic anhydrides; acetic anhydride, isocyanates, aldehydes, sodium peroxide. Strong reaction with toluene diisocyanate. Reacts with alkali metals and alkali earth metals. Attacks some plastics, rubber and coatings; copper and copper alloys.
Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration with provision for nitrogen oxides removal from flue gases by scrubber, catalytic or thermal device.
When using aniline, occupational workers should wear impervious protective clothing, including boots, gloves, laboratory coat, apron or coveralls, chemical safety goggles, and/ or a full face shield as appropriate, to prevent skin contact. Workplace facilities should maintain an eye-wash fountain and quick-drench facilities. Workers should not eat, drink, or smoke in the workplace.
Aniline Preparation Products And Raw materials
- 2-Anisidine-4-sulfonic acid
- m-Aminobenzene arsonic acid
- N-(4-CHLORO-PHENYL)-OXALAMIC ACID ETHYL ESTER
- N-METHYL-N-PHENYLCARBAMOYL CHLORIDE
- Diphenylcarbamyl chloride