CAS number 14901-63-4 N
PubChem 107908
ChemSpider 97035 N
MeSH Phosphorite
Gmelin Reference 68617
Jmol-3D images Image 1
Image 2
Molecular formula O3P3-
Molar mass 78.9720 g mol-1
Exact mass 78.958505378 g mol-1
Related compounds
Other anions Phosphinite


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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

A phosphite is a salt of phosphorous acid. The phosphite ion (PO33−) is a polyatomic ion with a phosphorus central atom where phosphorus has an oxidation state of +3.[2] Its molecular geometry is approximately tetrahedral like ammonia.[3]

Because phosphorous acid exists as an equilibrium tautomeric mixture of P(OH)3 and HP(O)(OH)2, predominantly the latter, there is some confusion in nomenclature. The IUPAC recommends[4] that the trihydroxy form be called phosphorous acid and its salts phosphites, with the dihydroxy form being called phosphonic acid and its salts phosphonates, but despite this, salts of HP(O)(OH)2 are often called phosphites rather than phosphonates.

The term phosphite is also used to mean phosphite ester, an organophosphorus compound with the formula P(OR)3.


Acid phosphites

Acid or hydrogen phosphites (which the IUPAC recommends be called acid or hydrogen phosphonates), such as NH4HP(O)2OH, can be prepared from phosphorous acid, HP(O)(OH)2.[2] Hydrogen bonding between anions leads to polymeric anionic structures. [3] Recently some others, RbHPHO3, CsHPHO3, TlHPHO3 have been prepared by reacting phosphorous acid with the metal carbonate. These compounds contain a layer polymeric anion consisting of HPO3 tetrahedra linked by hydrogen bonds. These layers are interleaved by layers of metal cations.[5]


Pyrophosphites (diphosphites) can be produced by gently heating acid phosphites under reduced pressure. They contain the ion, H2P2O52−which can be formulated [HP(O)2O−P(O)2H]2−.[2][3]

Naming of phosphite ions

The traditional name for HPO32− is phosphite, and for HPO2(OH) is hydrogenphosphite or acid phosphite. However IUPAC recommendations are that HPO32− is to be named hydrogenphosphite or phosphonate, HPO2(OH) is to be named dihydrogenphosphite or hydrogenphosphonate and phosphite is reserved for the hypothetical PO33− ion. [4]

Synthesis of phosphite esters

Organophosphorus compounds called phosphite esters (or sometimes just phosphites) have the formula (RO)3P. They are prepared by reacting phosphorus trichloride (or phosphorus tribromide) with an alcohol and a tertiary amine.

PCl3 + 3 ROH + 3 R'3N → P(OR)3 + 3R'3NHCl

Use in plants

Inorganic phosphites have been applied to crops to combat fungus-like pathogens of the order Oomycetes. The situation is confusing because of the similarity in name between phosphite and phosphate (a major plant nutrient and fertilizer ingredient), and controversial because phosphites have sometimes been advertised as fertilizers, even though they are converted to phosphate too slowly to serve as a plant's main phosphorus source. Lemoynie[6] and others[7] have described this complicated situation and noted that calling phosphites fertilizers avoided the regulatory complication and negative public perceptions that might have been incurred by registering them as fungicides.

See also

Further reading

  • A. Earnshaw, Norman Greenwood (1997). The Chemistry of the Elements - Second Edition. pp. 513–514. 


  1. ^ "Phosphorite - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information. 
  2. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  3. ^ a b c Crystal chemistry of inorganic phosphites, J. Loub, Acta Cryst. (1991), B47, 468-473, doi:10.1107/S0108768191002380
  4. ^ a b International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSCIUPAC. ISBN 0-85404-438-8. Electronic version..
  5. ^ Kosterina, E. V., Troyanov, S. I., Kemnitz, E. & Aslanov, L. A. (2001). "Synthesis and Crystal Structure of Acid Phosphites RbH2PO3, CsH2PO3, and TlH2PO3". Russian Journal of Coordination Chemistry 27 (7): 458–462. doi:10.1023/A:1011377229855. 
  6. ^ Phosphites and Phosphates: When Distributors and Growers alike could get confused! by Jean-Pierre Leymonie. Courtesy of New Ag International, September 2007 edition.
  7. ^ Thao; Yamakawa (2008). Soil Science and Plant Nutrition 55: 228–234. 

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Look at other dictionaries:

  • phosphite — [ fɔsfit ] n. m. • 1787; de phosphore ♦ Chim. Ester de l acide phosphoreux. ● phosphite nom masculin Sel ou ester de l acide phosphoreux. ⇒PHOSPHITE, subst. masc. CHIM. Sel ou ester de l acide phosphoreux. Phosphite acide de sodium NaH (PO3 H),… …   Encyclopédie Universelle

  • Phosphite — Phos phite, n. (Chem.) A salt of phosphorous acid. [1913 Webster] …   The Collaborative International Dictionary of English

  • Phosphite — bezeichnet: Salze der Phosphonsäure, siehe Phosphonate Ester der Phosphonsäure, siehe Phosphorigsäureester Diese Seite ist eine Begriffsklärung zur Unterscheidung mehrerer mit demselben Wort bezeichneter Begriffe …   Deutsch Wikipedia

  • Phosphīte — Phosphīte, Salze der phosphorigen Säure, z. B. Natriumphosphit, phosphorigsaures Natron …   Meyers Großes Konversations-Lexikon

  • Phosphite — Phosphīte, die phosphorigsauren Salze …   Kleines Konversations-Lexikon

  • phosphite — [fäs′fīt΄] n. [Fr: see PHOSPH(O) & ITE1] 1. a salt of phosphorous acid containing the trivalent, negative radical PO3 2. an uncharged ester of this acid …   English World dictionary

  • Phosphite — L ion phosphite (HPO32−) est un ion polyatomique avec un atome central de phosphore. Sa géométrie est pyramidale trigonale. De nombreux sels de phosphite, tels le phosphite d ammonium, sont hautement solubles dans l eau. Le terme… …   Wikipédia en Français

  • phosphite — fosfonatai statusas T sritis chemija formulė M₂PHO₃ atitikmenys: angl. phosphite; phosphonates rus. фосфит; фосфонаты ryšiai: sinonimas – fosfitas sinonimas – hidridotrioksofosfatas (2–) …   Chemijos terminų aiškinamasis žodynas

  • phosphite — noun Date: 1788 a salt or ester of phosphorous acid …   New Collegiate Dictionary

  • PHOSPHITE — n. m. T. de Chimie Combinaison de l’acide phosphoreux avec une base …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

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