Phenylarsonic acid is the organoarsenic 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 This colourless solid is an organic derivative of arsenic acid, AsO(OH)3, where one OH group has been replaced by a phenyl group.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 precursor to other arylarsonic acids.
Preparation and structure PhAsO3H2 can be prepared by several routes. A common method is the "Bart reaction", named for Heinrich Bart, in which phenyldiazonium salts react with sodium arsenite in the presence of a copper catalyst. The method is reminiscent of the Sandmeyer reaction. + NaAsO3H2 → C6H5AsO3H2 + Na+ + N2 Related derivatives are prepared similarly. It was first prepared by August Michaelis. X-ray crystallography shows short intermolecular O···O distances of 2.5 Å, consistent with hydrogen bonding. The arsenic center is tetrahedral.Struchkov, Yu. T. "Crystal and molecular structure of phenylarsonic acid" Russian Chemical Bulletin 1960, Volume 9, 1829-1833.
Related phenylarsonic acids Several derivatives of phenylarsonic acid were once used as poultry feed additives. These include 4-hydroxy-3-nitrobenzenearsonic acid (3-NHPAA, or Roxarsone), p-arsanilic acid (p-ASA), 4-nitrophenylarsonic acid (nitarsone, 4-NPAA), and p-ureidophenylarsonic acid (carbarsone, p-UPAA). They are now banned in the US and EU.
Further reading
References