Aniline

Source: Wikipedia, the free encyclopedia.
For other uses, see Aniline (disambiguation).
Not to be confused with the amino acid alanine, or annulene.
Aniline
Structural formula of aniline
Structural formula of aniline
Aniline
Aniline
Names
Preferred IUPAC name
Aniline[1]
Systematic IUPAC name
Benzenamine
Other names
Phenylamine
Aminobenzene
Benzamine
Identifiers
3D model (
JSmol
)
3DMet
605631
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.000.491 Edit this at Wikidata
EC Number
  • 200-539-3
2796
KEGG
RTECS number
  • BW6650000
UNII
UN number 1547
  • InChI=1S/C6H7N/c7-6-4-2-1-3-5-6/h1-5H,7H2 checkY
    Key: PAYRUJLWNCNPSJ-UHFFFAOYSA-N checkY
  • InChI=1/C6H7N/c7-6-4-2-1-3-5-6/h1-5H,7H2
    Key: PAYRUJLWNCNPSJ-UHFFFAOYAP
  • Nc1ccccc1
  • c1ccc(cc1)N
Properties
C6H5NH2
Molar mass 93.129 g·mol−1
Appearance Colorless liquid
Density 1.0297 g/mL
Melting point −6.30 °C (20.66 °F; 266.85 K)
Boiling point 184.13 °C (363.43 °F; 457.28 K)
3.6 g/(100 mL) at 20 °C
Vapor pressure 0.6 mmHg (20 °C)[2]
Acidity (pKa)
  • 4.63 (conjugate acid; H2O)[3]
−62.95·10−6 cm3/mol
1.58364
Viscosity 3.71
mPa·s
at 25 °C)
Thermochemistry
Std enthalpy of
combustion
(ΔcH⦵298)
 −3394 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 potential occupational carcinogen
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS08: Health hazardGHS09: Environmental hazardGHS07: Exclamation mark
Danger
H301, H311, H317, H318, H331, H341, H351, H372, H400
P201, P202, P260, P261, P264, P270, P271, P272, P273, P280, P281, P301+P310, P302+P352, P304+P340, P305+P351+P338, P308+P313, P310, P311, P312, P314, P321, P322, P330, P333+P313, P361, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
[5]
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 70 °C (158 °F; 343 K)
770 °C (1,420 °F; 1,040 K)
Explosive limits
 1.3–11%[2]
Lethal dose or concentration (LD, LC):
195 mg/kg (dog, oral)
250 mg/kg (rat, oral)
464 mg/kg (mouse, oral)
440 mg/kg (rat, oral)
400 mg/kg (guinea pig, oral)[4]
175 ppm (mouse, 7 h)[4]
250 ppm (rat, 4 h)
180 ppm (cat, 8 h)[4]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 5 ppm (19 mg/m3) [skin][2]
REL (Recommended)
 Ca [potential occupational carcinogen][2]
IDLH
(Immediate danger)
 100 ppm[2]
Related compounds
1-Naphthylamine
2-Naphthylamine
Related compounds
 Phenylhydrazine
Nitrosobenzene
Nitrobenzene
Supplementary data page
Aniline (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Aniline (from

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.[7]
It is toxic to humans.

Relative to benzene, it 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

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.

Structure

Ball-and-stick model of aniline from the crystal structure at 252 K

Aryl-N distances

In aniline, the C−N bond length is 1.41

3-methylaniline.[11]

Pyramidalization

The

delocalization of the N lone pair into the aryl ring favors planarity (a lone pair in a pure p orbital gives the best overlap with the orbitals of the benzene ring π system).[12][13]

Consistent with these factors, substituted anilines with electron donating groups are more pyramidalized, while those with electron withdrawing groups are more planar. In the parent aniline, the lone pair is approximately 12% s character, corresponding to sp7.3 hybridization.[12][clarification needed] (For comparison, alkylamines generally have lone pairs in orbitals that are close to sp3.)

The pyramidalization angle between the C–N bond and the bisector of the H–N–H angle is 142.5°.[14] For comparison, in more strongly pyramidal amine group in methylamine, this value is ~125°, while that of the amine group in formamide has an angle of 180°.

Production

Industrial aniline production involves two steps. First,

catalysts:[15] Approximately 4B kg are produced annually.[16]

The reduction of nitrobenzene to aniline was first performed by Nikolay Zinin in 1842, using sulfide salts (Zinin reaction). The reduction of nitrobenzene to aniline was also performed as part of reductions by Antoine Béchamp in 1854, using iron as the reductant (Bechamp reduction). These stoichiometric routes remain useful for specialty anilines.[17]

Aniline can alternatively be prepared from ammonia and phenol derived from the cumene process.[7]

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

safranine, which contains aniline and ortho-toluidine and is obtained from the distillate (échappés) of the fuchsine fusion.[18]

Related aniline derivatives

Many analogues and

4-chloroaniline.[7] Alternatively, using Buchwald-Hartwig coupling or Ullmann reaction approaches, aryl halides can be aminated with aqueous or gaseous ammonia.[19]

Reactions

The chemistry of aniline is rich because the compound has been cheaply available for many years. Below are some classes of its reactions.

Oxidation

Sample of 2,6-diisopropylaniline, a colorless liquid when pure, illustrating the tendency of anilines to air-oxidize to dark-colored products.

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,

4-aminophenol and para-amino diphenylamine.[18] Oxidation with persulfate affords a variety of polyanilines
. These polymers exhibit rich redox and acid-base properties.

Polyanilines can form upon oxidation of aniline.

Electrophilic reactions at ortho- and para- positions

Like phenols, 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 °C produces sulfanilic acid, H2NC6H4SO3H.

If bromine water is added to aniline, the

2,4,6-tribromoaniline is formed. To generate the mono-substituted product, a protection
with acetyl chloride is required:

Aniline can react with bromine even in room temperatures in water. Acetyl chloride is added to prevent tribromination.

The reaction to form 4-bromoaniline is to protect the amine with acetyl chloride, then hydrolyse back to reform aniline.

The largest scale industrial reaction of aniline involves its alkylation with formaldehyde. An idealized equation is shown:

2 C6H5NH2 + CH2O → CH2(C6H4NH2)2 + H2O

The resulting diamine is the precursor to

4,4'-MDI
and related diisocyanates.

Reactions at nitrogen

Basicity

Aniline is a weak

aliphatic amines. Aniline reacts with strong acids to form the anilinium (or phenylammonium) ion (C6H5−NH+3).[20]

Traditionally, the weak basicity of aniline is attributed to a combination of inductive effect from the more electronegative sp2 carbon and resonance effects, as the lone pair on the nitrogen is partially delocalized into the pi system of the benzene ring. (see the picture below):

The lone electron pair on the nitrogen delocalizes into the pi system of the benzene ring. This is responsible for nitrogen's weaker basicity compared to other amines.

Missing in such an analysis is consideration of solvation. Aniline is, for example, more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution.[21]

Acylation

Main article: Anilide

Aniline reacts with acyl chlorides such as acetyl chloride to give amides. The amides formed from aniline are sometimes called anilides, for example CH3−C(=O)−NH−C6H5 is acetanilide. At high temperatures aniline and carboxylic acids react to give the anilides.[22]

N-Alkylation

N-Methylation of aniline with

N,N-dimethylaniline
:

C6H5NH2 + 2 CH3OH → C6H5N(CH3)2 + 2H2O

N-Methylaniline and N,N-dimethylaniline are colorless liquids with boiling points of 193–195 °C and 192 °C, respectively. These derivatives are of importance in the color industry.

Carbon disulfide derivatives

Boiled with carbon disulfide, it gives sulfocarbanilide (diphenylthiourea) (S=C(−NH−C6H5)2), which may be decomposed into phenyl isothiocyanate (C6H5−N=C=S), and triphenyl guanidine (C6H5−N=C(−NH−C6H5)2).[18]

Diazotization

Aniline and its ring-substituted derivatives react with

hydroxyl (−OH), cyanide (−CN), or halide group (−X, where X is a halogen) via Sandmeyer reactions. This diazonium salt can also be reacted with NaNO2 and phenol to produce a dye known as benzeneazophenol, in a process called coupling
. The reaction of converting
primary aromatic
amine into diazonium salt is called diazotisation. In this reaction primary aromatic amine is allowed to react with sodium nitrite and 2 moles of HCl, which is known as "ice cold mixture" because the temperature for the reaction was as low as 0.5 °C. The benzene diazonium salt is formed as major product alongside the byproducts water and sodium chloride.

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

Nissl stain.[citation needed
]

In addition, aniline is the starting component in the production of diglycidyl aniline.[23] Epichlorohydrin is the other main ingredient.[23][24]

Uses

Aniline is predominantly used for the preparation of methylenedianiline and related compounds by condensation with formaldehyde. The diamines are condensed with phosgene to give methylene diphenyl diisocyanate, a precursor to urethane polymers.[7]

methylenedianiline
, a precursor to polyurethanes.

Other uses include

rubber processing chemicals (9%), herbicides (2%), and dyes and pigments (2%).[25] As additives to rubber, aniline derivatives such as phenylenediamines 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, the blue of blue jeans.[7]

Cake of indigo dye, which is prepared from aniline.

Aniline oil is also used for mushroom identification. Kerrigan's 2016 Agaricus of North America P45: (Referring to Schaffer's reaction) "In fact I recommend switching to the following modified test. Frank (1988) developed an alternative formulation in which aniline oil is combined with glacial acetic acid (GAA, essentially distilled vinegar) in a 50:50 solution. GAA is a much safer, less reactive acid. This single combined reagent is relatively stable over time. A single spot or line applied to the pileus (or other surface). In my experience the newer formulation works as well as Schaffer's while being safer and more convenient."[26]

History

Aniline was first isolated in 1826 by

Nikolay Nikolaevich Zinin reduced nitrobenzene and obtained a base that he named benzidam.[31] In 1843, August Wilhelm von Hofmann showed that these were all the same substance, known thereafter as phenylamine or aniline.[32]

Synthetic dye industry

In 1856, while trying to synthesise

aniline yellow.[35]

Further information: Nigrosene

Developments in medicine

In the late 19th century, derivatives of aniline such as

salvarsan – the first successful chemotherapy agent. Salvarsan's targeted microorganism, not yet recognized as a bacterium, was still thought to be a parasite, and medical bacteriologists, believing that bacteria were not susceptible to the chemotherapeutic approach, overlooked Alexander Fleming's report in 1928 on the effects of penicillin.[37]

In 1932,

topical use.) After World War II, Cornelius P. Rhoads introduced the chemotherapeutic approach to cancer treatment.[39]

Rocket fuel

Some early American rockets, such as the Aerobee and WAC Corporal, used a mixture of aniline and furfuryl alcohol as a fuel, with nitric acid as an oxidizer. The combination is hypergolic, igniting on contact between fuel and oxidizer. It is also dense, and can be stored for extended periods. Aniline was later replaced by hydrazine.[40]

Toxicology and testing

Aniline is toxic by inhalation of the vapour, ingestion, or percutaneous absorption.

Group 2A (Probably carcinogenic to humans), and it has specifically been linked to bladder cancer.[43]
Aniline has been implicated as one possible cause of forest dieback.[44]

Many methods exist for the detection of aniline.[45]

Oxidative DNA damage

Exposure of rats to aniline can elicit a response that is toxic to the

8-hydroxy-2'-deoxyguanosine (8-OHdG) in their DNA.[46] Although the base excision repair
pathway was also activated, its activity was not sufficient to prevent the accumulation of 8-OHdG. The accumulation of oxidative DNA damages in the spleen following exposure to aniline may increase mutagenic events that underlie tumorigenesis.

Notes

  1. ISBN 978-0-85404-182-4
    . Aniline, for C6H5-NH2, is the only name for a primary amine retained as a preferred IUPAC name for which full substitution is permitted on the ring and the nitrogen atom. It is a Type 2a retained name; for the rules of substitution see P-15.1.8.2. Substitution is limited to substituent groups cited as prefixes in accordance with the seniority of functional groups explicitly expressed or implied in the functional parent compound name. The name benzenamine may be used in general nomenclature.
  2. ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0033". National Institute for Occupational Safety and Health (NIOSH).
  3. ISBN 9781319079451
    .
  4. ^ a b c "Aniline". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. ^ "Aniline". cameochemicals.noaa.gov. US NOAA Office of Response and Restoration. Retrieved 2016-06-16.
  6. ^ "aniline | Etymology, origin and meaning of aniline by etymonline". www.etymonline.com. Retrieved 2022-02-15.
  7. ^
    OCLC 11469727
    .
  8. PMID 26852720
    .
  9. ISSN 2073-8994
    .
  10. doi:10.1002/9780470682531.pat0385
    .
  11. ISBN 9780470771662
    .
  12. ^
    OCLC 957525299.{{cite book}}: CS1 maint: location missing publisher (link
    )
  13. ^ Alabugin I. V.; Manoharan, M.; Buck, M.; Clark, R. J. Substituted Anilines: The Tug-Of-War between Pyramidalization and Resonance Inside and Outside of Crystal Cavities. THEOCHEM, 2007, 813, 21-27. http://dx.doi.org/10.1016/j.theochem.2007.02.016.
  14. OCLC 71790138
    .
  15. ^ Caskey, Douglas C.; Chapman, Douglas W. (Apr 24, 1985), Process for the preparation of arylhydroxylamines, retrieved 2016-06-16
  16. S2CID 3273484
    .
  17. ISBN 978-0-471-26418-7
    , retrieved 2022-02-01
  18. ^ a b c Chisholm 1911, p. 48.
  19. ^ "Aniline synthesis by amination (Arylation)".
  20. ISBN 0-534-16218-5
  21. ISBN 978-0-471-72091-1
  22. ^ Carl N. Webb (1941). "Benzanilide". Organic Syntheses; Collected Volumes, vol. 1, p. 82.
  23. ^
    ISBN 978-8178331829
    .
  24. S2CID 94372490
    .
  25. ^ "Aniline". The Chemical Market Reporter. Archived from the original on 2002-02-19. Retrieved 2007-12-21.
  26. ^ Kerrigan, Richard (2016). Agaricus of North America. NYBG Press. p. 45. ISBN 978-0-89327-536-5.
  27. doi:10.1002/andp.18260841109
    .
  28. ^ F. F. Runge (1834) "Ueber einige Produkte der Steinkohlendestillation" (On some products of coal distillation), Annalen der Physik und Chemie, 31: 65–77 (see page 65), 513–524; and 32: 308–332 (see page 331).
  29. ^ J. Fritzsche (1840) "Ueber das Anilin, ein neues Zersetzungsproduct des Indigo" (On aniline, a new decomposition product of indigo), Bulletin Scientifique [publié par l'Académie Impériale des Sciences de Saint-Petersbourg], 7 (12): 161–165. Reprinted in:
    • J. Fritzsche (1840) "Ueber das Anilin, ein neues Zersetzungsproduct des Indigo", Justus Liebigs Annalen der Chemie, 36 (1): 84–90.
    • J. Fritzsche (1840) "Ueber das Anilin, ein neues Zersetzungsproduct des Indigo", Journal für praktische Chemie, 20: 453–457. In a postscript to this article, Erdmann (one of the journal's editors) argues that aniline and the "cristallin", which was found by Unverdorben in 1826, are the same substance; see pages 457–459.
  30. ^ synonym I anil, ultimately from Sanskrit "nīla", dark-blue.
  31. ^ N. Zinin (1842). "Beschreibung einiger neuer organischer Basen, dargestellt durch die Einwirkung des Schwefelwasserstoffes auf Verbindungen der Kohlenwasserstoffe mit Untersalpetersäure" (Description of some new organic bases, produced by the action of hydrogen sulfide on compounds of hydrocarbons and hyponitric acid [H2N2O3]), Bulletin Scientifique [publié par l'Académie Impériale des Sciences de Saint-Petersbourg], 10 (18): 272–285. Reprinted in: N. Zinin (1842) "Beschreibung einiger neuer organischer Basen, dargestellt durch die Einwirkung des Schwefelwasserstoffes auf Verbindungen der Kohlenwasserstoffe mit Untersalpetersäure", Journal für praktische Chemie, 27 (1): 140–153. Benzidam is named on page 150. Fritzsche, Zinin's colleague, soon recognized that "benzidam" was actually aniline. See: Fritzsche (1842) Bulletin Scientifique, 10: 352. Reprinted as a postscript to Zinin's article in: J. Fritzsche (1842) "Bemerkung zu vorstehender Abhandlung des Hrn. Zinin" (Comment on the preceding article by Mr. Zinin), Journal für praktische Chemie, 27 (1): 153.
    See also: (Anon.) (1842) "Organische Salzbasen, aus Nitronaphtalose und Nitrobenzid mittelst Schwefelwasserstoff entstehend" (Organic bases originating from nitronaphthalene and nitrobenzene via hydrogen sulfide), Annalen der Chemie und Pharmacie, 44: 283–287.
  32. ^ August Wilhelm Hofmann (1843) "Chemische Untersuchung der organischen Basen im Steinkohlen-Theeröl" (Chemical investigation of organic bases in coal tar oil), Annalen der Chemie und Pharmacie, 47: 37–87. On page 48, Hofmann argues that krystallin, kyanol, benzidam, and aniline are identical.
  33. ^ A. Béchamp (1854) "De l'action des protosels de fer sur la nitronaphtaline et la nitrobenzine. Nouvelle méthode de formation des bases organiques artificielles de Zinin" (On the action of iron protosalts on nitronaphthaline and nitrobenzene. New method of forming Zinin's synthetic organic bases.), Annales de Chemie et de Physique, 3rd series, 42: 186 – 196. (Note: In the case of a metal having two or more distinct oxides (e.g., iron), a "protosalt" is an obsolete term for a salt that is obtained from the oxide containing the lowest proportion of oxygen to metal; e.g., in the case of iron, which has two oxides – iron (II) oxide (FeO) and iron (III) oxide (Fe2O3) – FeO is the "protoxide" from which protosalts can be made. See: Wiktionary: protosalt.)
  34. ^ Perkin, William Henry. 1861-06-08. "Proceedings of Chemical Societies: Chemical Society, Thursday, May 16, 1861". The Chemical News and Journal of Industrial Science. Retrieved on 2007-09-24.
  35. ^ Auerbach G, "Azo and naphthol dyes", Textile Colorist, 1880 May;2(17):137-9, p 138.
  36. ^ Wilcox RW, "The treatment of influenza in adults", Medical News, 1900 Dec 15;77():931-2, p 932.
  37. ^ a b c D J Th Wagener, The History of Oncology (Houten: Springer, 2009), pp 150–1.
  38. ^ John E Lesch, The First Miracle Drugs: How the Sulfa Drugs Transformed Medicine (New York: Oxford University Press, 2007), pp 202–3.
  39. ^ "Medicine: Spoils of War". Time. 15 May 1950. Archived from the original on 24 June 2013. Retrieved 20 November 2020.
  40. ^ Brian Burnell. 2016. http://www.nuclear-weapons.info/cde.htm#Corporal SSM
  41. ^ Muir, GD (ed.) 1971, Hazards in the Chemical Laboratory, The Royal Institute of Chemistry, London.
  42. ^ The Merck Index. 10th ed. (1983), p.96, Rahway: Merck & Co.
  43. PMID 21941546
    .
  44. ^ Krahl-Urban, B., Papke, H.E., Peters, K. (1988) Forest Decline: Cause-Effect Research in the United States of North America and Federal Republic of Germany. Germany: Assessment Group for Biology, Ecology and Energy of the Julich Nuclear Research Center.
  45. ^ Basic Analytical Toxicology (1995), R. J. Flanagan, S. S. Brown, F. A. de Wolff, R. A. Braithwaite, B. Widdop: World Health Organization
  46. ^
    PMID 18793663
    .

References

External links

Look up aniline in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Aniline.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Aniline&oldid=1218085232"