Thiosulfurous acid
Chemical compound
From Wikipedia, the free encyclopedia
Thiosulfurous acid is a hypothetical chemical compound with the formula HS−S(=O)−OH or HO−S(=S)−OH. Attempted synthesis leads to polymers.[3] It is a low oxidation state (+1) sulfur acid.[4] It is the Arrhenius acid for disulfur monoxide. Salts derived from thiosulfurous acid, which are also unknown, are named "thiosulfites", "thionosulfites" or "sulfurothioites". The ion is S=SO2−
2.
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| Names | |||
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| IUPAC names | |||
| Systematic IUPAC name
hydroxidooxidosulfanidosulfur[1] | |||
| Other names
sulfurothionous acid Thiothionyl hydroxide (minor tautomer) | |||
| Identifiers | |||
3D model (JSmol) |
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| ChEBI | |||
| ChemSpider | |||
| 184467 | |||
PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |||
| H2S2O2 | |||
| Molar mass | 98.14668 | ||
| Conjugate base | Thiosulfite | ||
| Related compounds | |||
Related compounds |
thiosulfuric acid SSO thiosulfinic acid | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structures
Other possible constitutional isomers are dihydroxydisulfane or hypodithionous acid HOSSOH, a linear chain, and thiothionyl hydroxide (S=S(OH)2) a tautomer where the hydrogen has moved from a sulfur to an oxygen.[5] The isomer with one hydrogen on sulfur and one on oxygen is the most stable according to calculations.[6] For HOSSOH, two different rotamers are possible, one with symmetry C1 and the other C2.[5]
Dithiosulfurous acid
The sulfur analog of thiosulfuric acid (HS−S(=O)2−OH), in which two sulfur atoms branch off of the central sulfur atom of a linear dihydrogen trisulfide structure (tetrathiosulfuric acid, (S=)2S(−SH)2 or (−S−)2S2+(−SH)2) has also been computationally studied.[7]
Reactions
It apparently decomposes to polysulfane oxide or polythionic acids in water, which is termed Wakenroder's liquid.[5]
In alkaline conditions thiosulfurous acid rapidly deteriorates forming a mixture of sulfide, sulfur, sulfite, and thiosulfate. In acidic conditions it will form hydrogen sulfide and sulfur dioxide as well. Some of these react to form pentathionate and other polythionates. Thiosulfurous acid reacts with sulfurous acid to give tetrathionate, and with thiosulfuric acid to make hexathionate.[8]
Esters
There are four possible R2S2O2 isomers (restricting sulfur to di- and tetravalence):
- (RO)2S=S
- A simple example is diethylthiosulfite, (EtO)2S=S, also known as diethylthionosulfite. It is stereochemically rigid on the NMR timescale to about 140 °C, somewhat similar to diethylsulfoxide.
- Many cyclic derivatives have been prepared from glycols. meso-Hydrobenzoin (PhCH(OH)−CH(OH)Ph) gives two stereoisomers; a third isomer results from d,l-PhCH(OH)−CH(OH)Ph.[9][10]
- ROSSOR
- Simple alkoxides react with disulfur dichloride to give the unbranched ROSSOR. They are immiscible in water, but dissolve in benzene or carbon tetrachloride.[8] These species are less rigid than thiosulfite-type esters.
- RS(O)2SR
- These compounds are the thiosulfonates.
- RS(O)SOR
- Disulfoxides are unstable, rearranging to the thiosulfonate.