Sulfur monoxide is an inorganic compound with formulaSO. It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 (disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.
The SO molecule has a triplet ground state similar to O2 and S2, that is, each molecule has two unpaired electrons.[2] The S−O bond length of 148.1 pm is similar to that found in lower sulfur oxides (e.g. S8O, S−O = 148 pm) but is longer than the S−O bond in gaseous S2O (146 pm), SO2 (143.1 pm) and SO3 (142 pm).[2]
The molecule is excited with near infrared radiation to the singlet state (with no unpaired electrons). 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.[3]
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:[4] as well as more complex examples, such as a trisulfide oxide, C10H6S3O.[5]
C2H4SO → C2H4 + SO
The SO molecule is thermodynamically unstable, converting initially to S2O2.[2]
SO inserts into alkenes, alkynes and dienes producing thiiranes, molecules with three-membered rings containing sulfur.[6]
Because of sulfur monoxide's rare occurrence in our atmosphere and poor stability, it is difficult to fully determine its hazards. But when condensed and compacted, it forms disulfur dioxide, which is relatively toxic and corrosive. This compound is also highly flammable (similar flammability to methane) and when burned produces sulfur dioxide, a poisonous gas.
SO converts to disulfur dioxide (S2O2).[23] Disulfur dioxide is a planar molecule with C2vsymmetry. The S−O bond length is 145.8 pm, shorter than in the monomer, and the S−S bond length is 202.45 pm. The O−S−S angle is 112.7°. S2O2 has a dipole moment of 3.17 D.[23]
^Salama, F.; Frei, H. J. (1989). "Near-Infrared-Light-Induced Reaction of Singlet SO with Allene and Dimethylacetylene in a Rare Gas Matrix. Infrared Spectra of Two Novel Episulfoxides". Journal of Physical Chemistry. 93: 1285–1292. doi:10.1021/j100341a023.
^Chao, P.; Lemal, D. M. (1973). "Sulfur Monoxide Chemistry. The Nature of SO from Thiirane Oxide and the Mechanism of Its Reaction with Dienes". Journal of the American Chemical Society. 95 (3): 920. doi:10.1021/ja00784a049.
^Grainger, R. S.; Procopio, A.; Steed, J. W. (2001). "A Novel Recyclable Sulfur Monoxide Transfer Reagent". Organic Letters. 3 (22): 3565–3568. doi:10.1021/ol016678g. PMID11678709.
^Nakayama, J.; Tajima, Y.; Piao, X.-H.; Sugihara, Y. (2007). "[1+2] Cycloadditions of Sulfur Monoxide (SO) to Alkenes and Alkynes and [1+4]Cycloadditions to Dienes (Polyenes). Generation and Reactions of Singlet SO?". Journal of the American Chemical Society. 129 (23): 7250–7251. doi:10.1021/ja072044e. PMID17506566.
^Suslick, K. S.; Flannigan, D. J. (2004). "The temperatures of single-bubble sonoluminescence (A)". The Journal of the Acoustical Society of America. 116 (4): 2540. Bibcode:2004ASAJ..116.2540S. doi:10.1121/1.4785135.
^Schenk, W. A. (1987). "Sulfur Oxides as Ligands in Coordination Compounds. Angewandte Chemie International Edition in English". 26: 98–109. doi:10.1002/anie.198700981. {{cite journal}}: Cite journal requires |journal= (help)
^Woollins, J. D. (1995). "Sulfur: Inorganic Chemistry". Encyclopedia of Inorganic Chemistry. John Wiley and Sons. ISBN0-471-93620-0.
^Na, C. Y.; Esposito, L. W.; Skinner, T. E. (1990). "International Ultraviolet Explorer observations of Venus SO2 and SO". Journal of Geophysical Research. 95: 7485–7491. Bibcode:1990JGR....95.7485N. doi:10.1029/JD095iD06p07485.
^Lis, D. C.; Mehringer, D. M.; Benford, D.; Gardner, M.; Phillips, T. G.; Bockelée-Morvan, D.; Biver, N.; Colom, P.; Crovisier, J.; Despois, D.; Rauer, H. (1997). "New Molecular Species in Comet C/1995 O1 (Hale–Bopp) Observed with the Caltech S submillimeter Observatory". Earth, Moon, and Planets. 78 (1–3): 13–20. Bibcode:1997EM&P...78...13L. doi:10.1023/A:1006281802554. S2CID51862359.
^Gottlieb, C. A.; Gottlieb, E. W.; Litvak, M. M.; Ball, J. A.; Pennfield, H. (1978). "Observations of interstellar sulfur monoxide". Astrophysical Journal. 1 (219): 77–94. Bibcode:1978ApJ...219...77G. doi:10.1086/155757.
^Moses, J. I.; Zolotov, M. Y.; Fegley, B. (2002). "Photochemistry of a Volcanically Driven Atmosphere on Io: Sulfur and Oxygen Species from a Pele-Type Eruption". Icarus. 156 (1): 76–106. Bibcode:2002Icar..156...76M. doi:10.1006/icar.2001.6758.
^Marvel, Kevin (1996). "NML Cygni". The Circumstellar Environment of Evolved Stars As Revealed by Studies of Circumstellar Water Masers. Universal Publishers. pp. 182–212. ISBN978-1-58112-061-5. Retrieved 23 August 2012.
^Balazy, M.; Abu-Yousef, I. A.; Harpp, D. N.; Park, J. (2003). "Identification of carbonyl sulfide and sulfur dioxide in porcine coronary artery by gas chromatography/mass spectrometry, possible relevance to EDHF". Biochemical and Biophysical Research Communications. 311 (3): 728–734. doi:10.1016/j.bbrc.2003.10.055. PMID14623333.
^ abLovas, F. J.; Tiemann, E.; Johnson, D. R. (1974). "Spectroscopic studies of the SO2 discharge system. II. Microwave spectrum of the SO dimer". The Journal of Chemical Physics. 60 (12): 5005–5010. Bibcode:1974JChPh..60.5005L. doi:10.1063/1.1681015.
