Phenylarsonic acid

Chembox new
ImageFile = PhAsO3H2.png ImageSize = 100px
IUPACName = Phenylarsonic acid
OtherNames = Benzenearsonic acid PAA
Section1 = Chembox Identifiers
CASNo = 98-05-5
PubChem =
SMILES =

Section2 = Chembox Properties
Formula = C₆H₇AsO₃
MolarMass = 202.05
Appearance = colourless solid
Density = 1.76 g/cm³
MeltingPt = 154–158° °C
BoilingPt =
Solubility = low
Section3 = Chembox Hazards
MainHazards = Toxic
FlashPt =
Autoignition =

Phenylarsonic acid is the chemical compound with the formula C₆H₅AsO(OH)₂, commonly abbreviated PhAsO₃H₂. This colourless solid is an organic derivative of arsenic acid, AsO(OH)₃, where one OH group has been replaced by a phenyl group.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

PhAsO₃H₂ 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. [Bullard, R. H.; Dickey, J. B. “Phenylarsonic Acid” Organic Syntheses, Collected Volume 2, pages 494 (1943). http://www.orgsyn.org/orgsyn/pdfs/CV2P0494.pdf] :C₆H₅N₂⁺ + NaAsO₃H₂ → C₆H₅AsO₃H₂ + Na⁺ + N₂Related derivatives are prepared similarly. [Ruddy, A. W.; Starkey, E. B. “p-Nitrophenylarsonic Acid” Organic Syntheses, Collected Volume 3, pp. 665 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0665.pdf] It was first prepared by Michaelis and Loenser. [cite journal
title = Ueber nitrirte Phenylarsenverbindungen
author = A. Michaelis, H. Loesner
journal = Berichte der deutschen chemischen Gesellschaft
volume = 27
issue =
pages = 263–272
year = 1877
url =
doi = 10.1002/cber.18940270151] [cite journal
title = Ueber aromatische Arsenverbindungen
author = A. Michaelis
journal = Berichte der deutschen chemischen Gesellschaft
volume = 8
issue =
pages = 1316–1317
year = 1875
url =
doi = 10.1002/cber.187500802125] [cite journal
title = Ueber die Verbindungen der Elemente der Stickstoffgruppe mit den Radicalen der aromatischen Reihe. Dritte Abhandlung: Ueber aromatische Arsenverbindungen
author = A. Michaelis, W. La Coste, A. Michaelis
journal = Annalen der Chemie
volume = 201
issue = 2-3
pages = 184–261
year = 1880
url =
doi = 10.1002/jlac.18802010204] X-ray crystallography indicates that the molecules are connected by hydrogen-bonds consistent with short distance of 2.5 Å separating the oxygen atoms. The arsenic center is tetrahedral. [Struchkov, Yu T. “Crystal and molecular structure of phenylarsonic acid” Russian Chemical Bulletin 1960, Volume 9, 1829-1833. DOI|10.1007/BF00907739]

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

External links