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Carbonyl sulfide

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Title: Carbonyl sulfide  
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Subject: Stratospheric sulfur aerosols, Sulfanyl, Carbon monoxide, Chinese drywall, Chugaev elimination
Collection: Hazardous Air Pollutants, Inorganic Carbon Compounds, Inorganic Sulfur Compounds, Oxides, Sulfides
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Carbonyl sulfide

Carbonyl sulfide
Carbonyl sulfide
Space-filling 3D model of carbonyl sulfide
CAS number  YesY
ChemSpider  YesY
EC number
Jmol-3D images Image 1
Molecular formula COS
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; 134.4 K)
Boiling point −50.2 °C (−58.4 °F; 223.0 K)
Solubility in water 0.376 g/100 mL (0 °C)
0.125 g/100 mL (25 °C)
Solubility very soluble in KOH, CS2
soluble in alcohol, toluene
Dipole moment 0.65 D
heat capacity
41.5 J/mol K
Std molar
231.5 J/mol K
Std enthalpy of
-141.8 kJ/mol
MSDS Carbonyl sulfide MSDS
EU Index Not listed
NFPA 704
Explosive limits 12-29%
Related compounds
Related compounds Carbon dioxide
Carbon disulfide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY   YesY/N?)

Carbonyl sulfide is 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]


  • Occurrence 1
  • Applications 2
  • Synthesis 3
  • Toxicity 4
  • References 5
  • Further reading 6
  • External links 7


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 CSO 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

  • Carbonyl sulfide and origins of life
  • Carbonyl sulfide as a potential fumigant
  • Carbonyl sulfide in the atmosphere

External links

  • Beck, M. T.; Kauffman, G. B. (1985). "COS and C3S2: The Discovery and Chemistry of Two Important Inorganic Sulfur Compounds".  
  • Svoronos P. D. N., Bruno T. J. (2002). "Carbonyl sulfide: A review of its chemistry and properties". Industrial & Engineering Chemistry Research 41 (22): 5321–5336.  

Further reading

  1. ^ a b c d "Carbonyl Sulfide CASRN: 463-58-1". Hazardous Substances Data Bank. National Library of Medicine. 
  2. ^ a b c d e f g "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.  
  4. ^ Leman, L.; Orgel, L.; Ghadiri, M. R.; Orgel; Ghadiri (2004). "Carbonyl Sulfide–Mediated Prebiotic Formation of Peptides".  
  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.  
  6. ^  
  7. ^ a b Seinfeld, J. (2006). Atmospheric Chemistry and Physics. London: J. Wiley.  
  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.  
  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.  
  10. ^ Pos,W and Berreshein,B. (1993). "Automotive tire wear as a source for atmospheric OCS and CS2". Geophysical Research Letter 1 (9): 815–818.  
  11. ^ Landis, G. A. (2003). "Astrobiology: the Case for Venus" (pdf). Journal of the British Interplanetary Society 56 (7–8): 250–254.  
  12. ^ Couërbe, J. P. (1841). "Ueber den Schwefelkohlenstoff". Journal für Praktische Chemie 23 (1): 83–124.  
  13. ^ Ferm R. J. (1957). "The Chemistry of Carbonyl Sulfide".  


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 1,400 ppm of COS for 90 minutes, or at 3,000 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]


KSCN + 2 H
+ H
+ NH

Carbonyl sulfide was first described in 1841,[12] 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 1,200 K (930 °C; 1,700 °F). A laboratory synthesis entails the reaction potassium thiocyanate and sulfuric acid. The resulting gas contains significant amounts of byproducts and requires purification.[13]


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.



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