Thiosulfuric acid
| Thiosulfuric acid | |
|---|---|
| |
| IUPAC name | sulfurothioic O-acid |
| Other names | thiosulfuric acid dihydroxidooxidosulfidosulfur |
| Identifiers[1] | |
| InChI | InChI=1/H2O3S2/c1-5(2,3)4/h(H2,1,2,3,4) |
| InChIKey | DHCDFWKWKRSZHF-UHFFFAOYAT |
| Standard InChI | InChI=1S/H2O3S2/c1-5(2,3)4/h(H2,1,2,3,4) |
| Standard InChIKey | DHCDFWKWKRSZHF-UHFFFAOYSA-N |
| CAS number | [] |
| PubChem | |
| Properties[1][2] | |
| Chemical formula | H2S2O3 |
| Molar mass | 114.14 g/mol |
| Melting point |
decomposes below 0 ºC |
| Solubility in water | decomposes |
| Acidity (pKa) | 0.6, 1.74 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Thiosulfuric acid is a sulfur oxoacid. The acid cannot be made by acidifying thiosulfate salts as the acid readily decomposes in water. The decomposition products can include sulfur, sulfur dioxide, hydrogen sulfide, polysulfanes, sulfuric acid and polythionates, depending on the exact reaction conditions.[3] Anhydrous methods of producing the acid were developed by Schmidt:[3][4]
- H2S + SO3 → H2S2O3·nEt2O (in diethyl ether at −78 °C )
- Na2S2O3 + 2HCl → 2NaCl + H2S2O3·2Et2O (in diethyl ether at −78 °C )
- HSO3Cl + H2S → HCl + H2S2O3 (low temperature)
The anhydrous acid also decomposes below 0 °C:[3]
- H2S2O3 → H2S + SO3
The S-acid isomer is believed to be more stable than the O-acid isomer based on Hartree–Fock/ab initio calculations with a 6-311 G** basis set and MP2 to MP4 refinements.[5] There is another isomeric form, a white crystalline adduct of hydrogen sulfide and sulfur trioxide, H2S·SO3, which can also be prepared at low temperature.[3]
References
- ↑ 1.0 1.1 Dictionary of Inorganic Compounds; Macintyre, Jane Elizabeth, Ed.; Chapman & Hall, 1992; p 3362. ISBN 0412301202.
- ↑ Page, F. M. The dissociation constants of thiosulphuric acid. J. Chem. Soc. 1953, 1719–24. DOI: 10.1039/JR9530001719.
- ↑ 3.0 3.1 3.2 3.3 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 846–48. ISBN 0-08-022057-6.
- ↑ Schmidt, Max Über Säuren des Schwefels. I. Zur Kenntnis der wasserfreien Thioschwefelsäure. Z. Anorg. Allg. Chem. 1957, 289, 141–57. DOI: 10.1002/zaac.19572890113.
- ↑ Miaskiewicz, Karol; Steudel, Ralf The Structures of Thiosulfuric Acid H2S2O3 and Its Monoanion HS2O3−. Angew. Chem., Int. Ed. Engl. 1992, 31 (1), 58–59. DOI: 10.1002/anie.199200581.
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