Heteropoly acid

A heteropoly acid is a class of acid made up of a particular combination of hydrogen and oxygen with certain metals and non-metals. This type of acid is a common re-usable acid catalyst in chemical reactions.[1]

To qualify as a heteropoly acid, the compound must contain:

The metal addenda atoms linked by oxygen atoms form a cluster with the hetero-atom inside bonded via oxygen atoms. Examples with more than one type of metal addenda atom in the cluster are well known. The conjugate anion of a heteropoly acid is known as a polyoxometalate.

Due to the possibilities of there being different combinations of addenda atoms and different types of hetero atoms there are a lot of heteropolyacids. Two of the better known groups of these are based on the Keggin, HnXM12O40, and Dawson, HnX2M18O62, structures.

Keggin structure, XM12O40n− Dawson structure, X2M18O62n−

Some examples are:

The heteropolyacids are widely used as homogeneous and heterogeneous catalysts,[2] particularly those based on the Keggin structure as they can possess qualities such as good thermal stability, high acidity and high oxidising ability. Some examples of catalysis are:[3]

Heteropolyacids have long been used in analysis and histology and are a component of many reagents e.g. the Folin-Ciocalteu reagent, folins phenol reagent used in the Lowry protein assay and EPTA, ethanolic phosphotungstic acid.

See also

Notes

  1. Mizuno, Noritaka; Misono, Makoto (1998). "Heterogeneous Catalysis". Chemical Reviews. 98: 199–217. doi:10.1021/cr960401q.
  2. Kozhevnikov, I. V. (1998). "Catalysis by heteropoly acids and multicomponent polyoxometalates in liquid-phase reactions". Chemical Reviews. 98 (1): 171–198. doi:10.1021/cr960400y. PMID 11851502.
  3. "Oxide catalysts in solid state chemistry". T Okuhara, M Misono. Encyclopedia of Inorganic Chemistry. Editor R Bruce King (1994). John Wiley and Sons. ISBN 0-471-93620-0

References

Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5 

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