Carbonyl sulfide

"COS" redirects here. For other uses, see COS (disambiguation).
Carbonyl sulfide
IUPAC name
Carbon oxide sulfide
463-58-1 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:16573 YesY
ChemSpider 9644 YesY
ECHA InfoCard 100.006.674
EC Number 207-340-0
KEGG C07331 YesY
PubChem 10039
Molar mass 60.075 g/mol
Appearance colorless gas
Odor sulfide-like
Density 2.51 g/L
Melting point −138.8 °C (−217.8 °F; 134.3 K)
Boiling point −50.2 °C (−58.4 °F; 223.0 K)
0.376 g/100 mL (0 °C)
0.125 g/100 mL (25 °C)
Solubility very soluble in KOH, CS2
soluble in alcohol, toluene
0.65 D
41.5 J/mol K
231.5 J/mol K
-141.8 kJ/mol
Safety data sheet Carbonyl sulfide MSDS
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Explosive limits 12-29%
Related compounds
Related compounds
Carbon dioxide
Carbon disulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Carbonyl sulfide is the organic compound with the formula OCS. Commonly written as COS, it is a colourless flammable gas with an unpleasant odor. It is a linear molecule consisting of a carbonyl group double bonded to a sulfur atom. Carbonyl sulfide can be considered to be intermediate between carbon dioxide and carbon disulfide, both of which are valence isoelectronic with it.

Carbonyl sulfide decomposes in the presence of humidity and bases to carbon dioxide and hydrogen sulfide.[1][2][3]

This compound is found to catalyze the formation of peptides from amino acids. This finding is an extension of the Miller–Urey experiment and it is suggested that carbonyl sulfide played a significant role in the origin of life.[4]


Carbonyl sulfide is the most abundant sulfur compound naturally present in the atmosphere, at 0.5±0.05 ppb, because it is emitted from oceans, volcanoes and deep sea vents. As such, it is a significant compound in the global sulfur cycle. Measurements on the Antarctica ice cores and from air trapped in snow above glaciers (firn air) have provided a detailed picture of OCS concentrations from 1640 to the present day and allow an understanding of the relative importance of anthropogenic and non-anthropogenic sources of this gas to the atmosphere.[5] Some carbonyl sulfide that is transported into the stratospheric sulfate layer is oxidized to sulfuric acid.[6] Sulfuric acid forms particulate which affects energy balance due to light scattering.[7] The long atmospheric lifetime of COS makes it the major source of stratospheric sulfate, though sulfur dioxide from volcanic activity can be significant too.[7] Carbonyl sulfide is also removed from the atmosphere by terrestrial vegetation by enzymes associated with the uptake of carbon dioxide during photosynthesis, and by hydrolysis in ocean waters.[8][9] Loss processes, such as these, limit the persistence (or lifetime) of a molecule of COS in the atmosphere to a few years.

The largest man-made sources of carbonyl sulfide release include its primary use as a chemical intermediate and as a byproduct of carbon disulfide production; however, it is also released from automobiles and its tire wear.,[10] coal-fired power plants, biomass combustion, fish processing, combustion of refuse and plastics, petroleum manufacture, and manufacture of synthetic fibers, starch, and rubber.[1] The average total worldwide release of carbonyl sulfide to the atmosphere has been estimated at about 3 million tons/year, of which less than one third was related to human activity.[1] It is also a significant sulfur-containing impurity in synthesis gas.

Carbonyl sulfide is present in foodstuffs, such as cheese and prepared vegetables of the cabbage family. Traces of COS are naturally present in grains and seeds in the range of 0.05–0.1 mg·kg−1.

Carbonyl sulfide has been observed in the interstellar medium (see also List of molecules in interstellar space), in comet 67P[11] and in the atmosphere of Venus, where, because of the difficulty of producing COS inorganically, it is considered a possible indicator of life.[12]


Carbonyl sulfide is used as an intermediate in the production of thiocarbamate herbicides.[2] Carbonyl sulfide is a potential alternative fumigant to methyl bromide and phosphine. In some cases, however, residues on the grain result in flavours that are unacceptable to consumers, e.g. barley used for brewing.


Carbonyl sulfide was first described in 1841,[13] but was apparently mischaracterized as a mixture of carbon dioxide and hydrogen sulfide. Carl von Than first characterized the substance in 1867. It forms when carbon monoxide reacts with molten sulfur. This reaction reverses above 1200 K (930 °C; 1700 °F). A laboratory synthesis entails the reaction potassium thiocyanate and sulfuric acid. The resulting gas contains significant amounts of byproducts and requires purification.[14]

KSCN + 2 H
+ H
+ NH


As of 1994, limited information existed on the acute toxicity of carbonyl sulfide in humans and in animals.[2] High concentrations (>1000 ppm) can cause sudden collapse, convulsions, and death from respiratory paralysis.[1][2] Occasional fatalities have been reported, practically without local irritation or olfactory warning.[2] In tests with rats, 50% animals died when exposed to 1400 ppm of COS for 90 minutes, or at 3000 ppm for 9 minutes.[2] Limited studies with laboratory animal studies also suggest that continued inhalation of low concentrations (~50 ppm for up to 12 weeks) does not affect the lungs or the heart.[2]


  1. 1 2 3 4 "Carbonyl Sulfide CASRN: 463-58-1". Hazardous Substances Data Bank. National Library of Medicine.
  2. 1 2 3 4 5 6 7 "Chemical Summary for Carbonyl Sulfide". U.S. Environmental Protection Agency.
  3. Protoschill-Krebs, G.; Wilhelm, C.; Kesselmeier, J. (1996). "Consumption of carbonyl sulphide (COS) by higher plant carbonic anhydrase (CA)". Atmospheric Environment. 30 (18): 3151–3156. Bibcode:1996AtmEn..30.3151P. doi:10.1016/1352-2310(96)00026-X.
  4. Leman L, Orgel L, Ghadiri MR (2004). "Carbonyl sulfide-mediated prebiotic formation of peptides". Science. 306 (5694): 283–6. Bibcode:2004Sci...306..283L. doi:10.1126/science.1102722. PMID 15472077.
  5. Montzka, S. A.; Aydin, M.; Battle, M.; Butler, J. H.; Saltzman, E. S.; Hall, B. D.; Clarke, A. D.; Mondeel, D.; Elkins, J. W. (2004). "A 350-year atmospheric history for carbonyl sulfide inferred from Antarctic firn air and air trapped in ice". Journal of Geophysical Research. 109 (D18): 22302. Bibcode:2004JGRD..10922302M. doi:10.1029/2004JD004686. eid D22302.
  6. Crutzen, P. (1976). "The possible importance of COS for the sulfate layer of the stratosphere". Geophysical Research Letters. 3 (2): 73–76. Bibcode:1976GeoRL...3...73C. doi:10.1029/GL003i002p00073.
  7. 1 2 Seinfeld, J. (2006). Atmospheric Chemistry and Physics. London: J. Wiley. ISBN 978-1-60119-595-1.
  8. Kettle, A. J.; Kuhn, U.; von Hobe, M.; Kesselmeier, J.; Andreae, M. O. (2002). "Global budget of atmospheric carbonyl sulfide: Temporal and spatial variations of the dominant sources and sinks". Journal of Geophysical Research. 107: 4658. Bibcode:2002JGRD..107.4658K. doi:10.1029/2002JD002187.
  9. Montzka, S. A.; Calvert, P.; Hall, B. D.; Elkins, J. W.; Conway, T. J.; Tans, P. P.; Sweeney, C. (2007). "On the global distribution, seasonality, and budget of atmospheric carbonyl sulfide (COS) and some similarities to CO2". Journal of Geophysical Research. 112 (D9): 9302. Bibcode:2007JGRD..11209302M. doi:10.1029/2006JD007665. eid D09302.
  10. Pos W, Berreshein B (1993). "Automotive tire wear as a source for atmospheric OCS and CS2". Geophysical Research Letters. 1 (9): 815–818. Bibcode:1993GeoRL..20..815P. doi:10.1029/93GL00972.
  11. Rosetta Blog. "OMET'S FIREWORK DISPLAY AHEAD OF PERIHELION". European Space Agency. Retrieved 11 August 2015.
  12. Landis, G. A. (2003). "Astrobiology: the Case for Venus" (pdf). Journal of the British Interplanetary Society. 56 (7–8): 250–254. Bibcode:2003JBIS...56..250L.
  13. Couërbe, J. P. (1841). "Ueber den Schwefelkohlenstoff". Journal für Praktische Chemie. 23 (1): 83–124. doi:10.1002/prac.18410230105.
  14. Ferm R. J. (1957). "The Chemistry of Carbonyl Sulfide". Chemical Reviews. 57 (4): 621–640. doi:10.1021/cr50016a002.

Further reading

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