View source for Aniline

{{Other uses}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 263518486
|   Name = Aniline
|   ImageFileL1 = Aniline.svg
|   ImageSizeL1 = 100px
|   ImageNameL1 = Aniline
|   ImageFileR1 = Aniline-3D-balls.png
|   ImageSizeR1 = 150px
|   ImageNameR1 = Aniline
|   IUPACName = Phenylamine
|   OtherNames = Phenylamine<br />Aminobenzene<br />Benzenamine
| Section1 = {{Chembox Identifiers
|   SMILES = NC1=CC=CC=C1
|   CASNo = 62-53-3
|    CASNo_Ref = {{cascite}}
  }}
| Section2 = {{Chembox Properties
|C=6|H=7|N=1
|   Appearance = colourless liquid
|   Density = 1.0217 g/ml, liquid
|   Solubility = 3.6 g/100 mL at 20°C
|   SolubleOther = methanol 10.97 M <ref>[http://oru.edu/cccda/sl/solubility/ugidata.php?solute=aniline&solvent=methanol Solubility of aniline in methanol]</ref>
|    Solvent = [[methanol]]
|   MeltingPtC = -6.3
|   BoilingPtC = 184.13
|   pKb = 9.3
|   pKa = 
|   Viscosity = 3.71 [[Poise|cP]] (3.71&nbsp;[[pascal second|mPa·s]] at 25&nbsp;°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 = {{R23/24/25}} {{R40}} {{R41}} {{R43}} {{R48/23/24/25}} {{R68}} {{R50}}
|   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]]
  }}
}}

'''Aniline''', '''phenylamine''' or '''aminobenzene''' is an [[organic compound]] with the [[Chemical formula|formula]] C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>.  Consisting of a [[benzene ring|phenyl group]] attached to an [[amino group]], aniline is the prototypical aromatic amine.  Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to [[polyurethane]]. Like most volatile amines, it possesses the somewhat unpleasant odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds.  Aniline is colorless, but it slowly [[organic oxidation|oxidizes]] and resinifies in air, giving a red-brown tint to aged samples.  

==Production==
Aniline is mainly produced in industry in two steps from [[benzene]].  First, benzene is [[nitration|nitrated]] using a concentrated mixture of [[nitric acid]] and [[sulfuric acid]] at 50 to 60 °C, which gives [[nitrobenzene]].  In the second step, the nitrobenzene is [[hydrogenation|hydrogenated]], typically at 200-300 °C in presence of various metal [[catalyst]]s:
:C<sub>6</sub>H<sub>5</sub>NO<sub>2</sub>  +  3 H<sub>2</sub>   →   C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>  +  2 H<sub>2</sub>O
Originally, the reduction was effected with a mixture of ferrous chloride and iron metal via the [[Bechamp reduction]].

As an alternative, aniline is also prepared from [[phenol]] and ammonia, the phenol being derived from the [[cumene process]].<ref name=Ullmann>Thomas Kahl, Kai-Wilfrid Schröder, F. R. Lawrence, W. J. Marshall, Hartmut Höke, Rudolf Jäckh "Aniline" in Ullmann's Encyclopedia of Industrial Chemistry 2007; John Wiley & Sons: New York.{{DOI|10.1002/14356007.a02_303}}</ref>

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.{{Citation needed|date=May 2010}}

===Related aniline derivatives===
Many derivatives of aniline can be prepared in similar fashion from nitrated aromatic compounds. Nitration followed by reduction of [[toluene]] affords [[toluidine]]s.  Nitration of chlorobenzene and related derivatives gives aniline derivatives, e.g. [[4-chloroaniline]].

==Reactions==
The chemistry of aniline is extremely rich because the compound has been cheaply available for many years.  Below are some classes of its reactions.
===Oxidation===
The oxidation of aniline has been heavily investigated, and can result in reactions localized at nitrogen or more commonly results in the formation of new C-N bonds. In alkaline solution, [[azobenzene]] results, whereas [[arsenic acid]] produces the violet-coloring matter violaniline. [[Chromic acid]] converts it into [[quinone]], whereas [[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]].  Oxidation with persulfate affords a variety of [[polyaniline]]s compounds. These polymers exhibit rich redox and acid-base properties.

===Electrophilic reactions at carbon===
Like [[phenol]]s, aniline derivatives are highly susceptible to [[electrophilic substitution]] reactions.  Its high reactivity reflects that it is an [[enamine]], which enhances the electron-donating ability of the ring.  For example, reaction of aniline with [[sulfuric acid]] at 180&nbsp;°C produces [[sulfanilic acid]], H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>SO<sub>3</sub>H, 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.  The largest scale industrial reaction of aniline involves its alkylation with [[formaldehyde]]:
:2 C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>  +  CH<sub>2</sub>O   →   CH<sub>2</sub>(C<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>)<sub>2</sub>  +  H<sub>2</sub>O
The resulting diamine is the precursor to [[4,4'-MDI]] and related diisocyanates.

===Reactions at nitrogen===
====Basicity====
Aniline is a weak [[base (chemistry)|base]]. [[Aromatic amine]]s such as aniline are, in general, much weaker bases than [[aliphatic]] amines because of the electron-withdrawing effect of the phenyl group. 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>).<ref>{{McMurry3rd}}</ref>  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. The weak basicity is due to a negative inductive effect as the lone pair on the nitrogen is partially delocalised into the pi system of the benzene ring.

====Acylation====
Aniline reacts with carboxylic acids<ref>{{OrgSynth | author = Carl N. Webb | title = Benzanilide | |collvol = 1 | collvolpages = 82 | year = 1941 | prep = cv1p0082}}</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 ([[acetanilide]]), an anti-pyretic and analgesic, is obtained by the reaction of [[acetic acid]] and aniline.

====''N''-Alkylation====
N-methylation of aniline with [[methanol]] at elevated temperatures over acid catalsts gives ''N''-methylaniline and [[dimethylaniline]]:
:C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>  +  2 CH<sub>3</sub>OH   →   C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>  +  H<sub>2</sub>O
Methyl and dimethylaniline are colourless liquids with [[boiling point|b.p.]] of 193-195 °C and 192 °C, respectively. These derivatives are of importance in the colour industry. Aniline combines directly with [[alkyl iodide]]s to form secondary and tertiary amines.

====Carbon disulfide 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>). 

====Diazotization====
Aniline and its ring-substituted derivatives react with [[nitrous acid]] to form [[diazonium salt]]s. Through these intermediates, 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]].  Hydrogenation gives [[cyclohexylamine]].

Being a standard reagent in laboratories, aniline is used for many niche reactions.  Its acetate is used in the [[Aniline acetate test]] for carbohydrates, identifying pentoses by conversion to [[furfural]].  It is used to stain neural [[RNA]] blue in the [[Nissl stain]].{{Citation needed|date=May 2010}}

==Uses==
The largest application of aniline is for the preparation of [[methylene diphenyl diisocyanate]] (MDI).  The majority of aniline serves this market. Other uses include [[rubber]] processing chemicals (9%), [[herbicides]] (2%), and dyes and pigments (2%).<ref name="CPoA">{{cite news|title=Aniline|publisher=The Chemical Market Reporter|url=http://www.the-innovation-group.com/ChemProfiles/Aniline.htm|accessdate=2007-12-21}}</ref>  As additives to rubber, aniline derivatives such as [[phenylenediamine]]{{dn}} and [[diphenylamine]], are antioxidants.  Illustrative of the drugs prepared from aniline is [[paracetamol]] (acetaminophen, [[Tylenol]]).  The principal use of aniline in the dye industry is as a precursor to [[indigo dye|indigo]], the blue of [[blue jeans]].<ref name=Ullmann/>

==History==
Aniline was first isolated from the destructive distillation of [[indigo dye|indigo]] in 1826 by [[Otto Unverdorben]]<ref>{{cite journal 
 | title = Ueber das Verhalten der organischen Körper in höheren Temperaturen
 | author = Otto Unverdorben
 | journal =  [[Annalen der Physik]]
 | volume = 84 
 | issue = 11 
 | pages = 397–410
 | year = 1826 
 | url =  
 | doi = 10.1002/andp.18260841109}}</ref> , who named it crystalline. In 1834, [[Friedrich Ferdinand Runge|Friedrich Runge]] (''Pogg. Ann.'', 1834, 31, p.&nbsp;65; 32, p.&nbsp;331) isolated from [[coal tar]] a substance that produced a beautiful blue colour on treatment with chloride of lime, which 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, from [[Portuguese language|Portuguese]] anil "the indigo shrub" from [[Arabic]] an-nil "the indigo" assimilated from al-nil, from Persian nila, from nili "indigo" with ''Indigofera anil'', anil being derived from the Sanskrit ''नीली'' ''nīla'', dark-blue, and ''nīlā'',<ref>http://www.etymonline.com/index.php?term=aniline</ref> 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.

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 an enormous range of dyestuffs, such as [[Magenta#Magenta dye (1860)|fuchsine]], safranine and induline. 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 Chemical 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.

==Toxicology==
Aniline is toxic by inhalation of the vapour.<ref name="HitCL">Muir, GD (ed.) 1971, ''Hazards in the Chemical Laboratory'', The Royal Institute of Chemistry, London.</ref>  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.  The early manufacture of aniline resulted in increased incidents of bladder cancer, but these effects are now attributed to naphthylamines, not anilines.<ref name=Ullmann/>

==References==
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<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.abc.chemistry.bsu.by/vi/aniline_electropolymerisation.htm Aniline electropolymerisation]
* [http://chem.sis.nlm.nih.gov/chemidplus/direct.jsp?name=Aniline&result=advanced  U.S. National Library of Medicine: ChemIDplus - Aniline] 

{{1911}}

[[Category:Aromatic amines]]
[[Category:Dyes]]
[[Category:Enamines]]
[[Category:Hazardous air pollutants]]
[[Category:IARC Group 3 carcinogens]]
[[Category:Arabic words and phrases]]

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