Sulfur monoxide is aninorganic compound withformulaSO. 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 toO2 andS2, that is, each molecule has two unpaired electrons.[2] The S−Obond length of 148.1 pm is similar to that found inlower sulfur oxides (e.g. S8O, S−O = 148 pm) but is longer than the S−O bond in gaseousS2O (146 pm),SO2 (143.1 pm) andSO3 (142 pm).[2]
The molecule is excited withnear 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 thatsinglet oxygen is more reactive thantriplet oxygen.[3]
The SO molecule is thermodynamically unstable, converting initially toS2O2.[2] Consequently controlled syntheses typically do not detect the presence of SO proper, but instead the reaction of achemical trap or the terminal decomposition products of S2O2 (sulfur andsulfur dioxide).
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 moleculeethylene episulfoxide:[4]
C2H4SO → C2H4 + SO
Yields directly from an episulfoxide are poor, and improve only moderately when the carbons are sterically shielded.[5] A much better approach decomposes a diaryl cyclic trisulfide oxide, C10H6S3O, produced fromthionyl chloride and the dithiol.[6]
SO converts to disulfur dioxide (S2O2).[22] Disulfur dioxide is a planar molecule withC2vsymmetry. 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.[22]
^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.
^Harpp, David N. (1997). "The sulfur diatomics".Phosphorus, Sulfur, and Silicon.120. Amsterdam, NL: Gordon & Breach: 53.doi:10.1080/10426509708545509.
^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.
^Magee, Philip S. (1971). "The Sulfur–Bromine Bond". In Senning, Alexander (ed.).Sulfur in Organic and Inorganic Chemistry. Vol. 1. New York: Marcel Dekker. pp. 271–276.ISBN0-8247-1615-9.LCCN70-154612.
^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.
^Lellouch, E. (1996). "Io's atmosphere: Not yet understood".Icarus.124: 1–21.doi:10.1006/icar.1996.0186.
^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. Retrieved23 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.
