Pyrosulfate
In chemistry, disulfate or pyrosulfate is the anion with the molecular formula {{chem|S|2|O|7|2−}}. Disulfate is the IUPAC name. {{RedBookRef|page=130}}
It has a dichromate-like structure and can be visualised as two corner-sharing SO4 tetrahedra, with a bridging oxygen atom.{{cite journal|title=The crystal structure determinations and refinements of K2S2O7, KNaS2O7 and Na2S2O7 from X-ray powder and single crystal diffraction data|author1=Ståhl, K.|author2=Balic-Zunic, T.|author3=da Silva, F.|author4=Eriksen, K.M.|author5=Berg, R.W.|author6=Fehrmann, R.|journal=Journal of Solid State Chemistry|volume=178|issue=10|pages=1697–1704|date=October 2005|doi=10.1016/j.jssc.2005.03.022|bibcode=2005JSSCh.178.1697S}}
In this anion, sulfur has an oxidation state of +6. Disulfate is the conjugate base of the hydrogen disulfate (hydrogen pyrosulfate) ion {{chem|HS|2|O|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:
:{{chem2|2 SO3 + ROH → ROSO2\sO\sSO3H}}
:{{chem2|ROSO2\sO\sSO3H -> ROSO3H + SO3}}
Several million tons are produced annually.{{cite book|doi=10.1002/14356007.a25_747.pub2 |chapter=Surfactants |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2019 |last1=Holmberg |first1=Krister |pages=1–56 |isbn=978-3-527-30673-2 }}