{{Chembox | ImageFileL1 = PhAsO3H2.png | ImageSizeL1 = 115 | ImageNameL1 = Stereo structural formula of phenylarsonic acid | ImageFileR1 = Phenylarsonic acid molecule ball.png | ImageSizeR1 = 135 | ImageAltR1 = Ball-and-stick model of the phenylarsonic acid molecule | PIN = Phenylarsonic acid | OtherNames = Benzenearsonic acid |Section1={{Chembox Identifiers | Abbreviations = PAA | CASNo = 98-05-5 | CASNo_Ref = {{cascite|correct|??}} | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 57F9KU116M | PubChem = 7365 | ChemSpiderID = 7087 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | EINECS = 202-631-9 | UNNumber = 1557 | MeSHName = Benzenearsonic+acid | ChEBI = 29851 | ChEMBL = 364571 | RTECS = CY3150000 | Beilstein = 2935741 | Gmelin = 131185 | SMILES = O[As](O)(=O)C1=CC=CC=C1 | StdInChI = 1S/C6H7AsO3/c8-7(9,10)6-4-2-1-3-5-6/h1-5H,(H2,8,9,10) | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = LVKZSFMYNWRPJX-UHFFFAOYSA-N | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}}} |Section2={{Chembox Properties | C=6 | H=7 | As=1 | O=3 | Appearance = Colourless solid | Density = 1.76 g cm<sup>−3</sup> | MeltingPtC = 154 to 158 | Solubility = low }} |Section3={{Chembox Hazards | MainHazards = Toxic }} }} '''Phenylarsonic acid''' is the chemical compound with the formula C<sub>6</sub>H<sub>5</sub>AsO(OH)<sub>2</sub>, commonly abbreviated PhAsO<sub>3</sub>H<sub>2</sub>. This colourless solid is an organic derivative of arsenic acid, AsO(OH)<sub>3</sub>, where one OH group has been replaced by a phenyl group. The compound is a buffering agent and a precursor to other organoarsenic compounds, some of which are used in animal nutrition, e.g. 4-hydroxy-3-nitrobenzenearsonic acid.

==Preparation and structure== PhAsO<sub>3</sub>H<sub>2</sub> can be prepared in several routes, but a common one entails treatment of phenyl diazonium salts with sodium arsenite (prepared from arsenious acid and base) in the presence of a copper(II) catalyst.<ref>Bullard, R. H.; Dickey, J. B. "Phenylarsonic Acid" Organic Syntheses, Collected Volume 2, pages 494 (1943). http://www.orgsyn.org/orgsyn/pdfs/CV2P0494.pdf</ref> :{{chem|C|6|H|5|N|2|+}} + NaAsO<sub>3</sub>H<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>AsO<sub>3</sub>H<sub>2</sub> + Na<sup>+</sup> + N<sub>2</sub> Related derivatives are prepared similarly.<ref>Ruddy, A. W.; Starkey, E. B. "''p''-Nitrophenylarsonic Acid" Organic Syntheses, Collected Volume 3, pp. 665 (1955). {{cite web |url=http://www.orgsyn.org/orgsyn/pdfs/CV3P0665.pdf |title=Archived copy |accessdate=2007-04-19 |url-status=dead |archiveurl=https://web.archive.org/web/20070930220515/http://www.orgsyn.org/orgsyn/pdfs/CV3P0665.pdf |archivedate=2007-09-30 }}</ref> It was first prepared by Michaelis and Loenser.<ref>{{cite journal | title = Ueber nitrirte Phenylarsenverbindungen |author1=A. Michaelis |author2=H. Loesner | journal = Berichte der Deutschen Chemischen Gesellschaft | volume = 27 | issue = | pages = 263–272 | year = 1877 | url = https://zenodo.org/record/1425738 | doi = 10.1002/cber.18940270151}}</ref><ref>{{cite journal | title = Ueber aromatische Arsenverbindungen | author = A. Michaelis | journal = Berichte der Deutschen Chemischen Gesellschaft | volume = 8 | issue = 2 | pages = 1316–1317 | year = 1875 | url = https://zenodo.org/record/1425084 | doi = 10.1002/cber.187500802125}}</ref><ref>{{cite journal | title = Ueber die Verbindungen der Elemente der Stickstoffgruppe mit den Radicalen der aromatischen Reihe. Dritte Abhandlung: Ueber aromatische Arsenverbindungen |author1=A. Michaelis |author2=W. La Coste |author3=A. Michaelis | journal = Annalen der Chemie | volume = 201 | issue = 2–3 | pages = 184–261 | year = 1880 | url = https://zenodo.org/record/1447359 | doi = 10.1002/jlac.18802010204}}</ref> X-ray crystallography indicates that the molecules are connected by hydrogen-bonds consistent with short distance of 2.5&nbsp;Å separating the oxygen atoms. The arsenic center is tetrahedral.<ref>Struchkov, Yu. T. "Crystal and molecular structure of phenylarsonic acid" Russian Chemical Bulletin 1960, Volume 9, 1829-1833. {{doi|10.1007/BF00907739}}</ref>

==Related phenylarsonic acids== Several derivatives of phenylarsonic acid have been used as additives for animal feeds. These include 4-hydroxy-3-nitrobenzenearsonic acid (3-NHPAA, or Roxarsone), ''p''-arsanilic acid (''p''-ASA), 4-nitrophenylarsonic acid (4-NPAA), and ''p''-ureidophenylarsonic acid (''p''-UPAA).

==References== <references/>

Category:Phenyl compounds Category:Arsonic acids