View source for Aniline

{{Chembox new
|   Name = Aniline
|   ImageFile = Aniline-2D-skeletal.png
|   ImageSize = 100px
|   ImageName = Aniline
|   ImageFile1 = Aniline-3D-vdW.png
|   ImageSize1 = 150px
|   ImageName1 = Aniline
|   OtherNames = Phenylamine<br />Aminobenzene
| Section1 = {{Chembox Identifiers
|   SMILES = NC1=CC=CC=C1
|   CASNo = 62-53-3
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>6</sub>H<sub>7</sub>N
|   MolarMass = 93.126 g/mol
|   Appearance = colorless liquid
|   Density = 1.0217 g/ml, liquid
|   Solubility = 3.6 g/100 mL at 20°C
|   MeltingPt = &minus;6.3 °C
|   BoilingPt = 184.13 °C
|   pKb = 9.40
|   Viscosity = 3.71 [[Poise|cP]] at 25 °C
  }}
| Section4 = {{Chembox Thermochemistry
|   DeltaHf = 
|   DeltaHc = -3394 kJ/mol
|   Entropy = 
  }}
| Section7 = {{Chembox Hazards
|   EUClass = Toxic ('''T''')<br />[[Carcinogen|Carc. Cat. 3]]<br />[[Mutagen|Muta. Cat. 3]]<br />Dangerous for<br />the environment ('''N''')
|   NFPA-H = 3
|   NFPA-F = 2
|   NFPA-R =
|   RPhrases = , 
|   SPhrases = {{S1/2}}, {{S26}}, {{S27}}, {{S36/37/39}}, {{S45}}, {{S46}}, {{S61}}, {{S63}}
  }}
| Section8 = {{Chembox Related
|   Function = [[aromatic amine]]s
|   OtherFunctn = [[1-Naphthylamine]]<br />[[2-Naphthylamine]]
|   OtherCpds = [[Phenylhydrazine]]<br />[[Nitrosobenzene]]<br />[[Nitrobenzene]]
  }}
}}
{{SI}}
{{CMG}}



==Overview==
'''Aniline''', '''phenylamine''' or '''aminobenzene''' is an [[organic compound]] with the [[Chemical formula|formula]] [[Carbon|C]]<sub>6</sub>[[Hydrogen|H]]<sub>5</sub>[[Nitrogen|N]][[Hydrogen|H]]<sub>2</sub>.  It is the simplest and one of the most imporant [[aromatic]] [[amine]]s, being used as a precursor to more complex chemicals.  Its main application is in the manufacture of [[polyurethane]]. Like most volatile [[amines]], it possesses a somewhat unpleasant odour of rotten fish and also has a burning aromatic taste; it is a highly [[wiktionary:acrid|acrid]] poison. It ignites readily, burning with a smoky flame.

==Structure and synthesis==
Consisting of a [[benzene ring|phenyl group]] attached to an [[amino group]], aniline is produced industrially in two steps from [[benzene]]:

[[Image:Aniline production.svg|none|450px]]

First, benzene is [[nitration|nitrated]] using a mixture of concentrated mixture of [[nitric acid]] and [[sulfuric acid]] at 50 - 60 °C, which gives the [[electrophile]] NO<sub>2</sub><sup>+</sup> that attacks the benzene, displacing a [[proton]] H<sup>+</sup> from that particular carbon atom.  The resulting [[nitrobenzene]] is then treated with hydrogen gas, typically at 600 °C in presence of a [[nickel]] [[catalyst]] to give aniline, this conversion being called [[hydrogenation]].

===Derivatives===
Many derivatives of aniline can be prepared similarly. In commerce three brands of aniline are distinguished—aniline oil for blue, which is pure aniline; aniline oil for red, a mixture of equimolecular quantities of aniline and ortho- and [[para-toluidine]]s; and aniline oil for [[safranine]], which contains aniline and ortho-[[toluidine]], and is obtained from the [[distillation|distillate]] (échappés) of the [[fuchsine]] fusion. 

==Properties==

===Oxidation===
Aniline is colourless, it slowly [[oxidizes]] and resinifies in air, giving a red-brown tint to aged samples.  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 [[4-aminophenol]] and para-amino [[diphenylamine]].

===Basicity===
Aniline is a weak [[base (chemistry)|base]]. [[Aromatic amine]]s such as aniline are generally much weaker bases than [[aliphatic]] amines. Aniline reacts with strong acids to form '''anilinium''' (or phenylammonium) ion (C<sub>6</sub>H<sub>5</sub>-NH<sub>3</sub><sup>+</sup>).  The [[sulfate]] forms beautiful white plates. Although aniline is weakly basic, it [[precipitates]] [[zinc]], [[aluminium]] and [[ferric]] salts, and on warming expels [[ammonia]] from its salts. 

===Acylation===
Aniline reacts with carboxylic acids<ref>Carl N. Webb "Benzanilid" Organic Syntheses, Collected Volume 1, p.82 (1941). http://www.orgsyn.org/orgsyn/pdfs/CV1P0082.pdf</ref> or more readily with [[acyl chloride]]s such as [[acetyl chloride]] to give [[amide]]s.  The amides formed from aniline are sometimes called "anilides", for example CH<sub>3</sub>-CO-NH-C<sub>6</sub>H<sub>5</sub> is [[acetanilide]].  [[Antifebrin]] or acetanilide is obtained from [[acetic acid]] and aniline. 

===N-alkyl derivatives===
Aniline combines directly with [[alkyl iodide]]s to form secondary and tertiary amines.  Monomethyl and dimethyl aniline are colourless liquids prepared by heating aniline, aniline hydro-chloride and [[methyl alcohol]] in an [[autoclave]] at 220 °C. They are of great importance in the colour industry. Monomethyl aniline boils at 193-195 °C, dimethyl aniline at 192 °C.

===Sulfur derivatives===
Boiled with [[carbon disulfide]], it gives sulfocarbanilide (diphenyl [[thiourea]]), CS(NHC<sub>6</sub>H<sub>5</sub>)<sub>2</sub>, which may be decomposed into phenyl [[isothiocyanate]], C<sub>6</sub>H<sub>5</sub>CNS, and triphenyl [[guanidine]], C<sub>6</sub>H<sub>5</sub>N=C(NHC<sub>6</sub>H<sub>5</sub>)<sub>2</sub>. 

Like [[phenols]], aniline derivatives are highly susceptible to [[electrophilic substitution]] reactions. For example, sulfonation of aniline produces sulfanilic acid, which can be converted to [[sulfanilamide]]. Sulfanilamide is one of the [[sulfonamide (medicine)|sulfa drug]]s which were widely used as [[antibacterial]]s in the early [[20th century]].  Reaction with [[sulfuric acid]] at 180&deg;C produces [[sulfanilic acid]], NH<sub>2</sub>C<sub>6</sub>H<sub>4</sub>SO<sub>3</sub>H. 

===Diazotization===
Aniline and its ring-substituted derivatives react with [[nitrous acid]] to form [[diazonium salt]]s. Through these, the -NH<sub>2</sub> group of aniline can be conveniently converted to -OH, -CN, or a [[halogen|halide]] via [[Sandmeyer reaction]]s.

===Other reactions===
It reacts with nitrobenzene to produce [[phenazine]] in the [[Wohl-Aue reaction]].

==Uses==
Originally the great commercial value of aniline was due to the readiness with which it yields, directly or indirectly, [[dye]]stuffs. The discovery of [[mauve]] in [[1856]] by [[Sir William Henry Perkin|William Henry Perkin]] was the first of a series of dyestuffs which are now to be numbered by hundreds. Reference should be made to the articles [[dyeing]], [[fuchsine]], [[safranine]], [[indulines]], for more details on this subject. In addition to its use as a precursor to dyestuffs, it is a starting-product for the manufacture of many drugs such as [[paracetamol]] (acetaminophen, [[Tylenol]]).

It is used to stain neural [[RNA]] blue in the [[Nissl stain]].

Currently the largest market for aniline is preparation of [[methylene diphenyl diisocyanate]] (MDI), some 85% of aniline serving this market. Other uses include [[rubber]] processing chemicals (9%), [[herbicides]] (2%), and dyes and pigments (2%).<ref name="CPoA">''Aniline producers price capacity market demand consumption production growth uses outlook'' n.d., The Chemical Market Reporter, Schnell Publishing Company. Retrieved January 12, 2002 from http://www.the-innovation-group.com/ChemProfiles/Aniline.htm</ref>

==History==
Aniline was first isolated from the destructive distillation of [[indigo dye|indigo]] in [[1826]] by [[Otto Unverdorben]] (''Pogg. Ann.'', 1826, 8, p. 397), who named it crystalline. In [[1834]], [[Friedrich Ferdinand Runge|Friedrich Runge]] (''Pogg. Ann.'', 1834, 31, p. 65; 32, p. 331) isolated from [[coal tar]] a substance which produced a beautiful blue colour on treatment with chloride of lime; this he named kyanol or cyanol. In [[1841]], C. J. Fritzsche showed that by treating indigo with caustic potash it yielded an oil, which he named aniline, from the specific name of one of the indigo-yielding plants, ''Indigofera anil'', anil being derived from the Sanskrit ''nīla'', dark-blue, and ''nīlā'', the indigo plant. About the same time [[Nikolay Nikolaevich Zinin|N. N. Zinin]] found that on reducing nitrobenzene, a base was formed which he named benzidam.  [[August Wilhelm von Hofmann]] investigated these variously prepared substances, and proved them to be identical ([[1855]]), and thenceforth they took their place as one body, under the name aniline or phenylamine.

Its first industrial-scale use was in the manufacture of [[mauveine]], a [[purple]] dye discovered in [[1856]] by Hofmann's student [[Sir William Henry Perkin|William Henry Perkin]]. At the time of mauveine's discovery, aniline was an expensive laboratory compound, but it was soon prepared "by the ton" using a process previously discovered by [[Antoine Béchamp]].<ref>Perkin, William Henry. [[1861]]-[[06-08]]. [http://books.google.com/books?pg=RA3-PA347&lpg=RA3-PA347&dq=roseine+fuchsine&source=web&sig=3ZzPC-IUshXCR79frTun3yNVOQ0&id=oKEEAAAAYAAJ&ots=B1-LmGtVMJ&output=text#PRA3-PA346,M1 "Proceedings of Checmical Societies: Chemical Society, Thursday, May 16, 1861."] ''The Chemical News and Journal of Industrial Science''. Retrieved on [[2007]]-[[09-24]].</ref> The synthetic dye industry grew rapidly as new aniline-based dyes were discovered in the late 1850s and 1860s.

[[p-Toluidine]], an aniline derivative, can be used in qualitative analysis to prepare carboxylic acid derivatives.

==Toxicology==
Aniline is toxic by inhalation of the vapour, absorption through the skin or swallowing. It causes headache, drowsiness, [[cyanosis]], mental confusion and in severe cases can cause [[seizure|convulsions]]. Prolonged exposure to the vapour or slight skin exposure over a period of time affects the nervous system and the blood, causing tiredness, loss of appetite, headache and dizziness.<ref name="HitCL">Muir, GD (ed.) 1971, ''Hazards in the Chemical Laboratory'', The Royal Institute of Chemistry, London.</ref>

Oil mixtures containing [[rapeseed|rapeseed oil]] denatured with aniline have been clearly linked by [[epidemiology|epidemiological]] and analytic chemical studies to the [[Toxic Oil Syndrome|toxic oil syndrome]] that hit [[Spain]] in the spring and summer of 1981, in which 20,000 became acutely ill, 12,000 were hospitalized, and more than 350 died in the first year of the epidemic. The precise [[etiology]] though remains unknown.

Some authorities class aniline as a [[carcinogen]], although the [[International Agency for Research on Cancer|IARC]] lists it in [[List of IARC Group 3 carcinogens|Group 3]] (''not classifiable as to its carcinogenicity to humans'') due to the limited and contradictory data available.

==References==
<references/>

==External links==
{{commons|Aniline|Aniline}}
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0011.htm International Chemical Safety Card 0011]
*[http://www.compchemwiki.org/index.php?title=Aniline Computational Chemistry Wiki entry]
*[http://www.abc.chemistry.bsu.by/vi/aniline_electropolymerisation.htm Aniline electropolymerisation]

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[[Category:Aromatic amines]]
[[Category:Dyes]]
[[Category:Hazardous air pollutants]]
[[Category:IARC Group 3 carcinogens]]

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