Phosphite
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/* Phosphorous acid */ Cleaned up one sentence, one spelling error
[[Image:Phosphite.png|thumb|right|The structure of a typical phosphite group.]]
The '''phosphite''' ion (PO<sub>3</sub><sup>3−</sup>) is a [[polyatomic ion]] with a [[phosphorus]] central atom. Its geometry is trigonal pyramidal. Many phosphite salts, such as ammonium phosphite, are highly water soluble. The term phosphite is sometimes used to mean [[phosphite ester]], an [[organophosphorus]] compound with the formula P(OR)<sub>3</sub>.
==Phosphorous acid==
The [[conjugate acid]] of the phosphite anion is [[phosphorous acid]] (H<sub>3</sub>PO<sub>3</sub>). Other names for this acid are orthophosphorous acid and dihydroxyphosphine oxide. H<sub>3</sub>PO<sub>3</sub> is also sometimes referred to as phosphorus trihydroxide and trihydroxyphosphine, though these names are misleading. Phosphorous acid is a diprotic acid, since the hydrogen bonded directly to the central phosphorus atom is not ionizable. Thus, a more logical chemical formula for phosphorous acid is HPO(OH)<sub>2</sub>, since only two hydroxy groups are actually present on the acid. The acid can be synthesized by treatment of a carboxylic acid, alcohol, or water, with [[phosphorus tribromide]] or more commonly [[phosphorus trichloride]].
PBr<sub>3</sub> + 3 [[Alcohol|ROH]] → 3 [[Alkyl halide|RBr]] + [[Phosphorous acid|HP(O)(OH)<sub>2</sub>]]
PBr<sub>3</sub> + 3 [[Carboxylic acid|RCOOH]] → 3 [[Acyl halide|RCOBr]] + [[Phosphorous acid|HP(O)(OH)<sub>2</sub>]]
PCl<sub>3</sub> + 3 H<sub>2</sub>O → [[Phosphorous acid|HP(O)(OH)<sub>2</sub>]] + 3 [[HCl]]
==Synthesis of phosphite compounds==
[[Organophosphorus compound]]s called [[phosphite ester]]s (or sometimes just phosphites) have the formula ([[Alkyl|R]]O)<sub>3</sub>P. They are prepared by reacting [[phosphorus trichloride]] (or [[phosphorus tribromide]]) with an [[alcohol]] and a tertiary [[amine]].
PCl<sub>3</sub> + 3 ROH + 3 R'<sub>3</sub>N → P(OR)<sub>3</sub> + 3R'<sub>3</sub>NHCl
Acid phosphites are compounds which contain a metal cation and a possible dihydrogen phosphite anion. These compounds are formed by reacting phosphorous acid with a metal [[carbonate]] (typically Rb, Cs, or Tl). Acid phosphites have crystalline structures consisting of alternating layers of HPO<sub>3</sub> tetrahedrons and metal cations.
==See also==
* [[Organophosphorus]]
* [[Phosphine]] - PR<sub>3</sub>
* [[Phosphine oxide]] - OPR<sub>3</sub>
* [[Phosphinite]] - P(OR)R<sub>2</sub>
* [[Phosphonite]] - P(OR)<sub>2</sub>R
* [[Phosphinate]] - OP(OR)R<sub>2</sub>
* [[Phosphonate]] - OP(OR)<sub>2</sub>R
* [[Phosphate]] - OP(OR)<sub>3</sub>
==References==
*{{cite book | title=The Chemistry of the Elements - Second Edition| author=A. Earnshaw, Norman Greenwood| year=1997| Page=513-514}}
*{{cite journal
|author=Kosterina, E. V., Troyanov, S. I., Kemnitz, E. & Aslanov, L. A.
|title=Synthesis and Crystal Structure of Acid Phosphites RbH2PO3, CsH2PO3, and TlH2PO3
|journal=Russian Journal of Coordination Chemistry
|year=2001|volume=27|pages=458–462
|doi=10.1023/A:1011377229855}}
[[Category:Functional groups]]
[[Category:Phosphorus compounds]]
[[Category:Organophosphorus]]
[[Category:Organophosphites]]
[[Category:Phosphites]]
[[Category:Oxoanions]]
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