{{Short description|Sulfur dianion}} thumb|right|Chemical structure of the disulfate anion
In chemistry, '''disulfate''' or '''pyrosulfate''' is the anion with the molecular formula {{chem|S|2|O|7|2−}}. Disulfate is the IUPAC name. <ref>{{RedBookRef|page=130}}</ref> It has a dichromate-like structure and can be visualised as two corner-sharing SO<sub>4</sub> tetrahedra, with a bridging oxygen atom.<ref>{{cite journal|title=The crystal structure determinations and refinements of K<sub>2</sub>S<sub>2</sub>O<sub>7</sub>, KNaS<sub>2</sub>O<sub>7</sub> and Na<sub>2</sub>S<sub>2</sub>O<sub>7</sub> 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}} </ref> 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.<ref name=UllmannSurf>{{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 }}</ref>
==See also== * Potassium pyrosulfate * Sodium pyrosulfate * Pyrophosphate * Pyrocarbonate
==References== {{reflist}}
Category:Pyrosulfates Category:Sulfur oxyanions