Dithionic acid

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Dithionic acid
Dithionic-acid-2D.png
Ball-and-stick model of dithionic acid
Identifiers
CAS number 14970-71-9 YesY
PubChem 26985
ChemSpider 25128 YesY
ChEBI CHEBI:29208 YesY
Jmol-3D images Image 1
Properties
Molecular formula H2S2O6
Molar mass 162.14 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Dithionic acid, H2S2O6, is a chemical compound known only in solution.[2]

Salts[edit]

Dithionic acid is dibasic and salts called dithionates are known. No acid salts have been discovered. All dithionates are readily soluble in water.[2] They are mild oxidizing and mild reducing agents. The structure of dithionate ion is like ethane, but two SO3 groups adopt an almost eclipsed conformation. The S—S length is 2.15 Å; S—O bonds are rather short with bond length of 1.43 Å.

Synthesis[edit]

Dithionates can be made by oxidizing a sulfite (from the +4 to the +5 oxidation state), but on a larger scale they are made by oxidizing a cooled aqueous solution of sulfur dioxide with MnO2:

2MnO2 + 3SO2 → MnS2O6 + MnSO4

The manganese dithionate solution formed can then be converted to dithionate salts of other metals by metathesis reactions:

Ba2+(aq) + MnS2O6(aq) + MnSO4(aq) → BaSO4(s)↓ + BaS2O6·2H2O(aq)

Concentrated solutions of dithionic acid can subsequently be obtained treating a barium dithionate solution with sulfuric acid:

BaS2O6(aq) + H2SO4(aq) → H2S2O6(aq) + BaSO4(s)↓

References[edit]

  1. ^ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSCIUPAC. ISBN 0-85404-438-8. p. 130. Electronic version.
  2. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.  pp. 715-716

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