Dihydroxydisulfane or hypodithionous acid is a reduced sulfur oxyacid with sulfur in a formal oxidation state of +1, but the valence of sulfur is 2. The structural formula is HO−S−S−OH, with all atoms arranged in a chain. It is an isomer of thiosulfurous acid but is lower in energy. Other isomers include HOS(=O)SH, HOS(=S)OH, and HS(=O)2SH. Disulfur monoxide, S2O, can be considered as the anhydride.[1] Unlike many of these other reduced sulfur acids, dihydroxydisulfane can be formed in a pure state by reacting hydrogen sulfide with sulfur dioxide at −70 °C in dichlorodifluoromethane.[2]
H2S + SO2 → H2S2O2
Dihyroxydisulfane may exist in an equilibrium with thiosulfurous acid.[3]
Organic derivatives such as dimethoxydisulfane,[4] diaceto disulfide,[5] and bis(trifluoroaceto) disulfide[6] also exist.
The conjugate bases are called disulfanediolate HS 2O− 2 and hypodithionite S 2O2− 2.
^Schmidt, Heinar; Steudel, Ralf; Suelzle, Detlev; Schwarz, Helmut (March 1992). "Sulfur compounds. 148. Generation and characterization of dihydroxy disulfide, HOSSOH: the chainlike isomer of thiosulfurous acid". Inorganic Chemistry. 31 (6): 941–944. doi:10.1021/ic00032a004.
^Makarov, Sergei V.; Makarova, Anna S.; Silaghi-Dumitrescu, Radu (2014). "Sulfoxylic and thiosulfurous acids and their dialkoxy derivatives". PATAI's Chemistry of Functional Groups. John Wiley & Sons. pp. 266–273. doi:10.1002/9780470682531.pat0829. ISBN9780470682531.