Sulfur monoxide

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Sulfur monoxide
Skeletal formula of sulfur monoxide
Skeletal formula of sulfur monoxide
Spacefill model of sulfur monoxide
Spacefill model of sulfur monoxide
Ball and stick model of sulfur monoxide
Names
IUPAC name
Sulfur monoxide[citation needed]
Systematic IUPAC name
Oxidosulfur[1]
Identifiers
3D model (
JSmol
)
7577656
ChEBI
ChEMBL
ChemSpider
666
MeSH sulfur+monoxide
  • InChI=1S/OS/c1-2 checkY
    Key: XTQHKBHJIVJGKJ-UHFFFAOYSA-N checkY
  • InChI=1/OS/c1-2
    Key: XTQHKBHJIVJGKJ-UHFFFAOYAK
  • O=S
Properties
SO
Molar mass 48.064 g mol−1
Appearance Colourless gas
Reacts
log P 0.155
Thermochemistry
221.94 J K−1 mol−1
Std enthalpy of
formation
(ΔfH⦵298)
 5.01 kJ mol−1
Related compounds
Related compounds
 Triplet oxygen
Disulfur
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Sulfur monoxide is an inorganic compound with formula SO. 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.

Structure and bonding

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 and reactions

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

thiiranes, molecules with three-membered rings containing sulfur.[6]

Generation under extreme conditions

In the laboratory, sulfur monoxide can be produced by treating sulfur dioxide with sulfur vapor in a glow discharge.[2] It has been detected in single-bubble sonoluminescence of concentrated sulfuric acid containing some dissolved noble gas.[7]

Benner and Stedman developed a chemiluminescence detector for sulfur via the reaction between sulfur monoxide and ozone:[8]

SO + O3 → SO2* + O2
SO2* → SO2 + hν

(* indicates an excited state)

Occurrence

Ligand for transition metals

As a ligand SO can bond in a number different ways:[9][10]

  • a terminal ligand, with a bent M−O−S arrangement, for example with titanium oxyfluoride[11]
  • a terminal ligand, with a bent M−S−O arrangement, analogous to bent
    nitrosyl
  • bridging across two or three metal centres (via sulfur), as in Fe3(μ3-S)(μ3-SO)(CO)9
  • η2 sideways-on (d–π interaction) with vanadium, niobium, and tantalum.[12]

Astrochemistry

Sulfur monoxide has been detected around Io, one of Jupiter's moons, both in the atmosphere[13] and in the plasma torus.[14] It has also been found in the atmosphere of Venus,[15] in Comet Hale–Bopp,[16] in 67P/Churyumov–Gerasimenko,[17] and in the interstellar medium.[18]

On Io, SO is thought to be produced both by volcanic and photochemical routes. The principal photochemical reactions are proposed as follows:[19]

O + S2 → S + SO
SO2 → SO + O

Sulfur monoxide has been found in NML Cygni.[20]

Biological chemistry

Sulfur monoxide may have some biological activity. The formation of transient SO in the

coronary artery of pigs has been inferred from the reaction products, carbonyl sulfide and sulfur dioxide.[21]

Safety measures

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.

Sulfur monoxide dication

benzene ring. The S−O bond length is 142.4(2) pm.[22]

C6(CH3)6 + SO2 + 3 HF·AsF5 → [C6(CH3)6SO][AsF6]2 + [H3O][AsF6]

Disulfur dioxide

The structure of disulfur dioxide, S2O2
A space-filling model of the disulfur dioxide molecule
Main article: Disulfur dioxide

SO converts to disulfur dioxide (S2O2).

D.[23]

References

  1. ^ "sulfur monoxide (CHEBI:45822)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute.
  2. ^
    ISBN 978-0-08-037941-8
    .
  3. doi:10.1021/j100341a023
    .
  4. doi:10.1021/ja00784a049
    .
  5. PMID 11678709
    .
  6. PMID 17506566
    .
  7. doi:10.1121/1.4785135
    .
  8. S2CID 98849015
    .
  9. doi:10.1002/anie.198700981. {{cite journal}}: Cite journal requires |journal= (help
    )
  10. ISBN 0-471-93620-0
    .
  11. S2CID 201617509
    .
  12. S2CID 73438027
    .
  13. doi:10.1006/icar.1996.0186
    .
  14. PMID 10720321
    .
  15. doi:10.1029/JD095iD06p07485
    .
  16. S2CID 51862359
    .
  17. ^ "Астрономический вестник. T. 54, Номер 2, 2020".
  18. doi:10.1086/155757
    .
  19. doi:10.1006/icar.2001.6758
    .
  20. ISBN 978-1-58112-061-5
    . Retrieved 23 August 2012.
  21. PMID 14623333
    .
  22. S2CID 27260554
    .
  23. ^
    doi:10.1063/1.1681015
    .
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