View source for Arsanilic acid

{{chembox
|   Name = 
|   ImageFile = ArsanilicTaut.png
|   ImageSize = 300
|   ImageName = Chemical structure of arsanilic acid
|   ImageFile1 = P-arsanilic-acid-from-xtal-3D-balls.png
|   ImageSize1 = 200px
|   ImageName1 = Ball-and-stick model of the solid-state zwitterionic structure of arsanilic acid
|   IUPACName = 4-aminophenylarsonic acid
|   OtherNames = 4-Aminobenzenearsonic acid, 4-Aminophenylarsonic acid, 4-Arsanilic acid, Atoxyl
| Section1 = {{Chembox Identifiers
|   SMILES = 
|   CASNo = 98-50-0
|   ChemSpiderID = 
|   RTECS = 
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>6</sub>H<sub>8</sub>AsNO<sub>3</sub>
|   MolarMass = 217.054 g/mol
|   Appearance = white solid
|   Density = 1.957 g/cm<sup>3</sup>
|   Solubility = modest
|   Solvent = other solvents
|   SolubleOther = 
|   MeltingPt = 232 °C
|   BoilingPt = 
|   pKa = 
|   Viscosity = 
  }}
| Section3 = {{Chembox Structure
|   CrystalStruct =
|   Dipole =
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| Section7 = {{Chembox Hazards
|   ExternalMSDS =
|   MainHazards = Toxic
|   NFPA-H = 2
|   NFPA-F = 0
|   NFPA-R = 0
|   FlashPt = 
|   RPhrases = {{R23}}-{{R25}},{{R50}}-{{R53}}	23/25-50/53
|   SPhrases = {{S20}}{{S21}}{{S28}}{{S45}}{{S60}}-{{S61}}
  }}
| Section8 = {{Chembox Related
|   Function = 
|   OtherFunctn = 
|   OtherCpds = [[phenylarsonic acid]]
  }}
}}

'''Arsanilic acid''' is the [[organoarsenic compound]] also called ''p''-aminophenylarsenic acid. This colourless solid was used as a drug in the late 19th and early 20th centuries but is now considered prohibitively toxic.  Arsanilic acid is a derivative of [[phenylarsonic acid]] with an [[amine]] in the 4-position.  It exists as a [[zwitterion]], H<sub>3</sub>N<sup>+</sup>C<sub>6</sub>H<sub>4</sub>AsO<sub>3</sub>H<sup>&minus;</sup>,<ref>{{cite journal | author = R. H. Nuttall and W. N. Hunter | title = ''p-Arsanilic Acid, a Redetermination | journal = [[Acta Cryst.]] | year = 1996 | volume = C52 | pages = 1681–1683 | doi = 10.1107/S010827019501657X}}</ref> although it is typically represented with the non-zwitterionic formula, H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>AsO<sub>3</sub>H<sub>2</sub>.

==Synthesis==
Arsanilic acid was first reported in 1859 by [[Antoine Béchamp]]. Béchamp optimistically chose the name ''Atoxyl,'' referring to its reduced toxicity compared to arsenic.  The original synthesis, which involved the reaction of [[aniline]] and [[arsenic acid]], remains useful today:<ref>{{OrgSynth | author = W. Lee Lewis and H. C. Cheetham | title = Arsanilic Acid | collvol = 1 | collvolpages = 70 | year = 1941 | prep = CV1P0070}}</ref>

:C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>  +  H<sub>3</sub>AsO<sub>4</sub>  →  H<sub>2</sub>O<sub>3</sub>AsC<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>  +  H<sub>2</sub>O

==History and uses==
Arsanilic acid was initially used in medicine to treat simple [[skin disease]]s. In 1905, two British physicians, H.W. Thomas and A. Breinl, reported that atoxyl was active against the trypanosomes of [[African trypanosomiasis|sleeping sickness]].  The effect was however not very pronounced and the necessary [[Effective dose|dosage]] was so high that [[toxicity|toxic]] side effects far outweighed the benefits.  It frequently caused [[blindness]] by damaging the [[optic nerve]] and other varied disorders.  Nevertheless, the discovery of arsanilic acid's activity against [[trypanosomes]] was the basis for a major advance by the bacteriologist [[Paul Ehrlich]].  Ehrlich, who believed that the formula was incorrect, and the organic chemist Alfred Bertheim revised the structural assignment. The correct formula suggested new ways that the atoxyl molecule could be modified, and a series of such derivatives were then synthesized.  Testing for anti-[[syphilis|syphilitic]] activity was performed by [[Sahachiro Hata]] who worked in Ehrlich's lab.  The result of this collaboration was the discovery of the drug [[Salvarsan]] in 1909, which also was later abandoned but which accelerated the growth of medicinal chemistry.

Although the practice is controversial, arsanilic acid and related compounds are sometimes used in treating [[dysentery]] in swine.

==References==
{{reflist}}

==External links==
* [http://www.chemheritage.org/EducationalServices/pharm/chemo/readings/ehrlich/pabio.htm Atoxyl at Chemical Heritage] More about the origins and uses of the medicine.
* [http://stevenlehrer.com/explorers/chapter_7.htm Explorers of the Body] Some info about sleeping sickness and atoxyl.
* [http://preview.pesticideinfo.org/Detail_ChemReg.jsp?Rec_Id=PC37540 Arsonic Acid poisoning information].
* Ihde, Aaron J. ''The Development of Modern Chemistry'',  Dover, New York, 1984. pp. 697-698.

[[Category:Organoarsenic compounds]]
[[Category:Aromatic amines]]

[[ar:أتوكسيل]]
[[de:Natriumhydrogenarsanilat]]
[[zh:对氨基苯胂酸]]
[[Category:2Fix]]