Disulfur dioxide

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Disulfur dioxide
structure of disulfur dioxide, S2O2
space-filling model of the disulfur dioxide molecule
Other names
SO dimer
3D model (JSmol)
Molar mass 96.1299 g/mol
Appearance gas
Main hazards toxic
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur.[2] The solid is unstable with a lifetime of a few seconds at room temperature.[3]


Disulfur dioxide adopts cis-planar structure with C2v symmetry. The S-O bond length is 145.8 pm, shorter than in sulfur monoxide. The S-S bond length is 202.45 pm and the OSS angle is 112.7°. S2O2 has a dipole moment of 3.17 D.[4] an asymmetric top molecule.[1][5]


Sulfur monoxide (SO) converts to disulfur dioxide (S2O2) spontaneously and reversibly.[4] So the substance can be generated by methods that produce sulfur monoxide. Disulfur dioxide has also been formed by an electric discharge in sulfur dioxide.[5] Another laboratory procedure is to react oxygen atoms with carbonyl sulfide or carbon disulfide vapour.[6]

Although most forms of elemental sulfur (S8 and other rings and chains) do not combine with SO2, atomic sulfur does so to form sulfur monoxide, which dimerizes:[7]

S + SO2 S2O2
S2O2 ⇌ 2SO

Disulfur dioxide is also produced upon a microwave discharge in sulfur dioxide diluted in helium.[8] At a pressure of 0.1 mm Hg, five percent of the result is S2O2.[9]

Disulfur dioxide is formed transiently when hydrogen sulfide and oxygen undergo flash photolysis.[10]


The ionisation energy of disulfur dioxide is 9.93±0.02  eV.[6]

Disulfur dioxide absorbs at 320–400 nm, as observed of the Venusian atmosphere,[11] and is believed to have contributed to the greenhouse effect on that planet.[12]


Although disulfur dioxide exists in equilibrium with sulfur monoxide, it also reacts with sulfur monoxide to form sulfur dioxide and disulfur monoxide.[8][13]


S2O2 can be a ligand with transition metals. It binds in the η2-S,S' position with both sulfur atoms linked to the metal atom.[14] This was first shown in 2003. The bis-(trimethylphosphine) thiirane S-oxide complex of platinum, when heated in toluene at 110 °C loses ethylene, and forms a complex with S2O2: (Ph3P)2PtS2O2.[15] Iridium atoms can also form a complex: cis-[(dppe)2IrS2]Cl with sodium periodate oxidises to [(dppe)2IrS2O] and then to [(dppe)2IrS2O2], with dppe being 1,2-Bis(diphenylphosphino)ethane.[16][17] This substance has the S2O2 in a cis position. The same conditions can make a trans complex, but this contains two separate SO radicals instead. The iridium complex can be decomposed with triphenyl phosphine to form triphenyl phosphine oxide, and triphenyl phosphine sulfide.[16]


The S2O2 anion has been observed in the gas phase. It may adopt a trigonal shape akin to SO3.[18]



Transition Frequency MHz[5]
21,1−20,2 11013.840
41,3−40,4 14081.640
11,1−00,0 15717.946
40,4−31,3 16714.167
31,3−20,2 26342.817
42,2−41,3 26553.915
22,0−21,1 28493.046
60,6−51,5 30629.283
52,4−51,5 35295.199
51,5−40,4 35794.527

In the Solar System[edit]

There is a some evidence that disulfur dioxide may be a small component in the atmosphere of Venus, and that it may substantially contribute of the planet's severe greenhouse effect.[11] It is not found in any substantive quantity in Earth's atmosphere.


  1. ^ a b Demaison, Jean; Vogt, Jürgen (2011). "836 O2S2 Disulfur dioxide" (PDF). Asymmetric Top Molecules, Part 3. Landolt-Börnstein - Group II Molecules and Radicals. 29D3. Springer. p. 492. doi:10.1007/978-3-642-14145-4_258. ISBN 978-3-642-14145-4.
  2. ^ Arnold F. Holleman; Egon Wiber; Nils Wiberg, eds. (2001). "Oxides of sulfur". Inorganic Chemistry. Academic Press. p. 530. ISBN 9780123526519.
  3. ^ Mitchell, Stephen C. (3 September 2004). Biological Interactions Of Sulfur Compounds. CRC Press. p. 7. ISBN 978-0203362525.
  4. ^ a b Lovas, F. J. (1974). "Spectroscopic studies of the SO2 discharge system. II. Microwave spectrum of the SO dimer". The Journal of Chemical Physics. 60: 5005. doi:10.1063/1.1681015.
  5. ^ a b c Thorwirth, Sven; P. Theulé; C. A. Gottlieb; H. S. P. Müller; M. C. McCarthy; P. Thaddeus (23 February 2006). "Rotational spectroscopy of S2O: vibrational satellites, 33 S isotopomers, and the submillimeter-wave spectrum" (PDF). Journal of Molecular Structure. 795 (1–3): 219–229. Bibcode:2006JMoSt.795..219T. doi:10.1016/j.molstruc.2006.02.055.
  6. ^ a b Cheng, Bing-Ming; Wen-Ching Hung (1999). "Photoionization efficiency spectrum and ionization energy of S[sub 2]O[sub 2]". The Journal of Chemical Physics. 110 (1): 188. Bibcode:1999JChPh.110..188C. doi:10.1063/1.478094. ISSN 0021-9606.
  7. ^ Murakami, Yoshinori; Shouichi Onishi; Takaomi Kobayashi; Nobuyuki Fujii; Nobuyasu Isshiki; Kentaro Tsuchiya; Atsumu Tezaki; Hiroyuki Matsui (2003). "High Temperature Reaction of S + SO2→ SO + SO: Implication of S2O2Intermediate Complex Formation". The Journal of Physical Chemistry A. 107 (50): 10996–11000. Bibcode:2003JPCA..10710996M. doi:10.1021/jp030471i. ISSN 1089-5639.
  8. ^ a b Field, T A; A E Slattery; D J Adams; D D Morrison (2005). "Experimental observation of dissociative electron attachment to S2O and S2O2 with a new spectrometer for unstable molecules" (PDF). Journal of Physics B: Atomic, Molecular and Optical Physics. 38 (3): 255–264. Bibcode:2005JPhB...38..255F. doi:10.1088/0953-4075/38/3/009. ISSN 0953-4075. Archived from the original (PDF) on 2015-09-24. Retrieved 2013-05-13.
  9. ^ Pujapanda, Balaram Sahoo, Nimain C. Nayak, Asutosh Samantaray, Prafulla K.; Balaram, Sahoo; Charan, nayak Nimai; samantaray Asutosh; pujapanda Prafulla Kumar (2012). Inorganic Chemistry. PHI Learning Pvt. Ltd. p. 461. ISBN 9788120343085. Retrieved 16 May 2013.
  10. ^ Compton, R. G.; Bamford, C.H.; Tipper, C.F.H. (1972). "Oxidation of H2S". Reactions of Non-Metallic Inorganic Compounds. Comprehensive Chemical Kinetics. Elsevier. p. 50. ISBN 978-0080868011.
  11. ^ a b BN Frandsen; PO Wennberg; HG Kjaergaard (2016). "Identification of OSSO as a near-UV absorber in the Venusian atmosphere" (PDF). Geophys. Res. Lett. 43 (21): 11, 146. Bibcode:2016GeoRL..4311146F. doi:10.1002/2016GL070916.
  12. ^ "Rare molecule on Venus may help explain planet's weather - Technology & Science - CBC News". Cbc.ca. Retrieved November 11, 2016.
  13. ^ Herron, J. T.; R. E. Huie (1980). "Rate constants at 298 K for the reactions sulfur monoxide + sulfur monoxide + M -> dimeric sulfur monoxi de + M and sulfur monoxide + dimeric sulfur monoxide -> sulfur dioxide + sulfur oxide (S2O)". Chemical Physics Letters. 76 (2): 322–324. Bibcode:1980CPL....76..322H. doi:10.1016/0009-2614(80)87032-1.
  14. ^ Halcrow, Malcolm A.; John C. Huffman; George Christou (1994). "Synthesis, Characterization, and Molecular Structure of the New S2O Complex Mo(S2O)(S2CNEt2)3.cntdot.1/2Et2O" (PDF). Inorganic Chemistry. 33 (17): 3639–3644. doi:10.1021/ic00095a005. ISSN 0020-1669.
  15. ^ Lorenz, Ingo-Peter; Jürgen Kull (1986). "Complex Stabilization of Disulfur Dioxide in the Fragmentation of ThiiraneS-Oxide on Bis(triphenylphosphane)platinum(0)". Angewandte Chemie International Edition in English. 25 (3): 261–262. doi:10.1002/anie.198602611. ISSN 0570-0833.
  16. ^ a b Schmid, Günter; Günter Ritter; Tony Debaerdemaeker (1975). "Die Komplexchemie niederer Schwefeloxide, II. Schwefelmonoxid und Dischwefeldioxid als Komplexliganden". Chemische Berichte. 108 (9): 3008–3013. doi:10.1002/cber.19751080921. ISSN 0009-2940.
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  18. ^ Clements, Todd G.; Hans-Jürgen Deyerl; Robert E. Continetti (2002). "Dissociative Photodetachment Dynamics of S2O2-" (PDF). The Journal of Physical Chemistry A. 106 (2): 279–284. Bibcode:2002JPCA..106..279C. doi:10.1021/jp013329v. ISSN 1089-5639. Retrieved 2013-05-13.