Pyrosulfate

Chemical structure of the disulfate anion

In chemistry, disulfate or pyrosulfate is the anion with the molecular formula S
₂O^2−
₇. Disulfate is the IUPAC name. [1] It has a dichromate-like structure and can be visualised as two corner-sharing SO₄ tetrahedra, with a bridging oxygen atom.[2] In this anion, sulfur has an oxidation state of +6. Disulfate is the conjugate base of the hydrogen disulfate (hydrogen pyrosulfate) ion HS
₂O^−
₇, which in turn is the conjugate base of disulfuric acid (pyrosulfuric acid).

Role in sulfation

Industrial production of sulfate ester-based surfactants involves the reaction (sulfation) of fatty alcohols with sulfur trioxide. For example, dodecyl alcohol is sulfated using sulfur trioxide. The reaction proceeds by initial formation of the pyrosulfate:

2 SO₃ + ROH → ROSO₂−O−SO₃H

ROSO₂−O−SO₃H → ROSO₃H + SO₃

Several million tons are produced annually.[3]

See also

• Potassium pyrosulfate
• Sodium pyrosulfate
• Pyrophosphate
• Pyrocarbonate

References

1. International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 130. Electronic version.
2. Ståhl, K.; Balic-Zunic, T.; da Silva, F.; Eriksen, K.M.; Berg, R.W.; Fehrmann, R. (October 2005). "The crystal structure determinations and refinements of K₂S₂O₇, KNaS₂O₇ and Na₂S₂O₇ from X-ray powder and single crystal diffraction data". Journal of Solid State Chemistry. 178 (10): 1697–1704. Bibcode:2005JSSCh.178.1697S. doi:10.1016/j.jssc.2005.03.022.
3. Holmberg, Krister (2019). "Surfactants". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–56. doi:10.1002/14356007.a25_747.pub2. ISBN 978-3-527-30673-2.