Thiosulfuric acid is the inorganic compound with the formula H2S2O3. It has attracted academic interest as a simple, easily accessed compound that is labile. It has few practical uses.
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| IUPAC name
Sulfurothioic S-acid[3]
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| Systematic IUPAC name
Dihydroxidooxidosulfidosulfur[3] | |
| Other names
Thiosulfuric acid
Sulfurothioic O,O-acid[2] | |
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CompTox Dashboard (EPA)
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| Properties[1][5] | |
| H2S2O3 | |
| Molar mass | 114.13 g·mol−1 |
| Melting point | decomposes below 0 °C |
| decomposes | |
| Acidity (pKa) | |
| Conjugate base | Thiosulfate |
| Related compounds | |
Other cations
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation and degradation
editThe acid cannot be made by acidifying aqueous thiosulfate salt solutions 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 reaction conditions.[6] Anhydrous methods of producing the acid were developed by Max Schmidt:[6][7]
- H2S + SO3 → H2S2O3
- Na2S2O3 + 2 HCl → 2 NaCl + H2S2O3
- HSO3Cl + H2S → HCl + H2S2O3
The anhydrous acid also decomposes above −5 °C:[6]
- H2S2O3 → H2S + SO3
Structure
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The isomer (O=)2S(−OH)(−SH) is more stable than the isomer (O=)(S=)S(−OH)2 as established by Hartree–Fock/ab initio calculations with a 6-311 G** basis set and MP2 to MP4 refinements.[8][clarification needed] The theoretically predicted structure conforms with the double bond rule.
An isomer of thiosulfuric acid is the adduct of hydrogen sulfide and sulfur trioxide, H2S·SO3, which can also be prepared at low temperature. It is a white crystalline solid.[6]
References
edit- ^ a b Macintyre, Jane Elizabeth, ed. (1992), Dictionary of Inorganic Compounds, Chapman & Hall, p. 3362, ISBN 0-412-30120-2
- ^ ACD Chemsketch Name Free
- ^ a b International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 139. Electronic version.
- ^ a b 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 239. ISBN 0-08-029214-3. LCCN 82-16524.
- ^ Page, F. M. (1953), "The dissociation constants of thiosulphuric acid", J. Chem. Soc.: 1719–24, doi:10.1039/JR9530001719
- ^ a b c d Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 846–48. ISBN 978-0-08-022057-4..
- ^ Schmidt, Max (1957), "Über Säuren des Schwefels. I. Zur Kenntnis der wasserfreien Thioschwefelsäure", Z. Anorg. Allg. Chem., 289 (1–4): 141–57, doi:10.1002/zaac.19572890113
- ^ a b Miaskiewicz, Karol; Steudel, Ralf (1992), "The Structures of Thiosulfuric Acid H
2S
2O
3 and Its Monoanion HS
2O−
3", Angew. Chem. Int. Ed. Engl., 31 (1): 58–59, doi:10.1002/anie.199200581