Dithionic acid

Last updated
Dithionic acid
Dithionic-acid-2D.png
Dithionic-acid-3D-balls.png
Names
IUPAC name
dithionic acid [1]
Other names
hypodisulfuric acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
PubChem CID
UNII
  • InChI=1S/H2O6S2/c1-7(2,3)8(4,5)6/h(H,1,2,3)(H,4,5,6) Yes check.svgY
    Key: RMGVZKRVHHSUIM-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/H2O6S2/c1-7(2,3)8(4,5)6/h(H,1,2,3)(H,4,5,6)
    Key: RMGVZKRVHHSUIM-UHFFFAOYAM
  • O=S(=O)(O)S(=O)(=O)O
Properties
H2S2O6
Molar mass 162.14 g mol−1
Acidity (pKa)−3.4 (estimated) [2]
Conjugate base Dithionate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Dithionic acid, H2S2O6, is the inorganic compound with the formula H2S2O6. It is the doubly protonated derivative of dithionate, a well-characterized dianion. Dithionic acid is mainly observed and characterized as an aqueous solution. [3]

Contents

Synthesis

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 manganese dioxide:

2 MnO2 + 3 SO2 → 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· 2 H2O (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)↓

See also

References

  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. Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 63. ISBN   0-08-029214-3. LCCN   82-16524.
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN   978-0-08-037941-8. pp. 715-716