Peroxydiphosphoric acid

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Peroxydiphosphoric acid
Peroxodiphosphorsäure - Peroxodiphosphoric acid.svg
Names
Other names
peroxodiphosphoric acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
  • InChI=1S/H4O8P2/c1-9(2,3)7-8-10(4,5)6/h(H2,1,2,3)(H2,4,5,6)
    Key: NUGJFLYPGQISPX-UHFFFAOYSA-N
  • InChI=1S/H4O8P2/c1-9(2,3)7-8-10(4,5)6/h(H2,1,2,3)(H2,4,5,6)
  • OP(=O)(O)OOP(=O)(O)O
Properties
H4P2O8
Molar mass 193.97 g/mol
Related compounds
Related compounds
peroxymonophosphoric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Peroxydiphosphoric acid (H4P2O8) is an oxyacid of phosphorus. Its salts are known as peroxydiphosphates. It is one of two peroxyphosphoric acids, along with peroxymonophosphoric acid.

History[edit]

Both peroxyphosphoric acids were first synthesized and characterized in 1910 by Julius Schmidlin and Paul Massini,[1] where peroxydiphosphoric acid was obtained in poor yields from the reaction between diphosphoric acid and highly-concentrated hydrogen peroxide.

Preparation[edit]

Peroxydiphosphoric acid can be prepared by the reaction between phosphoric acid and fluorine, with peroxymonophosphoric acid being a by-product.[2]

The compound is not commercially available and must be prepared as needed.[2] Peroxodiphosphates can be obtained by electrolysis of phosphate solutions.[3]

Properties[edit]

Peroxydiphosphoric acid is a tetraprotic acid, with acid dissociation constants given by pKa1 ≈ −0.3, pKa2 ≈ 0.5, pKa3 = 5.2 and pKa4 = 7.6.[4] In aqueous solution, it disproportionates upon heating to peroxymonophosphoric acid and phosphoric acid.[5]

References[edit]

  1. ^ Schmidlin, Julius; Massini, Paul (1910). "Phosphormonopersäure und Überphosphorsäure". Ber. Dtsch. Chem. Ges. 43 (1): 1162–1171. doi:10.1002/cber.191004301195.
  2. ^ a b Harald, Jakob; Leininger, Stefan; Lehmann, Thomas; Jacobi, Sylvia; Gutewort, Sven (2007). "Peroxo Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Wiley‐VCH Verlag. pp. 310–311. doi:10.1002/14356007.a19_177.pub2. ISBN 9783527306732.
  3. ^ Riedel, Erwin (2004). Anorganische Chemie (6 ed.). Berlin/New York: de Gruyter. p. 493.
  4. ^ Crutchfield, Marvin M.; Edwards, John O. (1960). "The Acidity and Complexes of Peroxydiphosphoric Acid". J. Am. Chem. Soc. 82 (14): 3533–3537. doi:10.1021/ja01499a015.
  5. ^ Kolditz, Lothar (1983). Anorganische Chemie. Vol. 1. Berlin: Deutscher Verlag der Wissenschaften. p. 437.