Sulfur monoxide
Sulfur monoxide is an inorganic compound with formula. It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2. It has been detected in space but is rarely encountered intact otherwise.
Structure and bonding
The SO molecule has a triplet ground state similar to O2 and S2, that is, each molecule has two unpaired electrons. The S−O bond length of 148.1 pm is similar to that found in lower sulfur oxides but is longer than the S−O bond in gaseous S2O, SO2 and SO3.The molecule is excited with near infrared radiation to the singlet state. The singlet state is believed to be more reactive than the ground triplet state, in the same way that singlet oxygen is more reactive than triplet oxygen.
Production and reactions
The SO molecule is thermodynamically unstable, converting initially to S2O2. Consequently controlled syntheses typically do not detect the presence of SO proper, but instead the reaction of a chemical trap or the terminal decomposition products of S2O2.Production of SO as a reagent in organic syntheses has centred on using compounds that "extrude" SO. Examples include the decomposition of the relatively simple molecule ethylene episulfoxide:
Yields directly from an episulfoxide are poor, and improve only moderately when the carbons are sterically shielded. A much better approach decomposes a diaryl cyclic trisulfide oxide, C10H6S3O, produced from and thionyl chloride.
SO inserts into alkenes and alkynes to produce thiirane oxides and thiirene S-oxides respectively. It reacts with dienes to produce S-oxides.
Sulfur monoxide may form transiently during the metallic reduction of thionyl bromide.
Generation under extreme conditions
In the laboratory, sulfur monoxide can be produced by treating sulfur dioxide with sulfur vapor in a glow discharge. It has been detected in single-bubble sonoluminescence of concentrated sulfuric acid containing some dissolved noble gas.Benner and Stedman developed a chemiluminescence detector for sulfur via the reaction between sulfur monoxide and ozone:
Occurrence
Ligand for transition metals
are well-known. One example is Fe39.Astrochemistry
Sulfur monoxide has been detected around Io, one of Jupiter's moons, both in the atmosphere and in the plasma torus. It has also been found in the atmosphere of Venus, in Comet Hale–Bopp, in 67P/Churyumov–Gerasimenko, and in the interstellar medium.On Io, SO is thought to be produced both by volcanic and photochemical routes. The principal photochemical reactions are proposed as follows:
Sulfur monoxide has been found in NML Cygni.