Triphosphoric acid

Triphosphoric acid (also tripolyphosphoric acid), with formula H5P3O10, is a condensed form of phosphoric acid. In the family of phosphoric acids, it is the next polyphosphoric acid after pyrophosphoric acid, H4P2O7, also called diphosphoric acid.

Triphosphoric acid
Structure of triphosphoric acid
Names
IUPAC name
Diphosphono hydrogenphosphate
Systematic IUPAC name
Triphosphoric acid
Tripolyphosphoric acid
Other names
Diphosphonophosphoric acid
Phosphono trihydrogenpyrophosphate
Phosphonopyrophosphoric acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.752
EC Number
  • 233-840-3
KEGG
UNII
  • InChI=1S/H5O10P3/c1-11(2,3)9-13(7,8)10-12(4,5)6/h(H,7,8)(H2,1,2,3)(H2,4,5,6) ☒N
    Key: UNXRWKVEANCORM-UHFFFAOYSA-N ☒N
  • OP(=O)(O)OP(=O)(O)OP(=O)(O)O
Properties
H5P3O10
Molar mass 257.95 g/mol
Acidity (pKa) See body
Conjugate base Triphosphate
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Corrosive (C)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Compounds such as ATP (adenosine triphosphate) are esters of triphosphoric acid.

Triphosphoric acid has not been obtained in crystalline form. The equilibrium mixture with an overall composition corresponding to H5P3O10 contains about 20% of triphosphoric acid. A solution of the pure species can be obtained by ion exchange of the sodium salt, sodium triphosphate, at 0 °C.[1]

Triphosporic acid is a pentaprotic acid, meaning that it can release five protons in basic enough conditions. Sources differ on the corresponding pKa values:

  • 1.0; 2.2; 2.3; 5.7; 8.5[1]
  • 1.0; 2.2; 2.3; 3.7; 8.5[2]
  • small; small; 2.30; 6.50; 9.24

References
  1. Corbridge, D. (1995). "Chapter 3: Phosphates". Studies in inorganic Chemistry vol. 20. Elsevier Science B.V. pp. 169–305. ISBN 0-444-89307-5.
  2. Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, p. 729, ISBN 0-12-352651-5
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