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Carbonyl sulfide
Carbonyl sulfide
Space-filling 3D model of carbonyl sulfide
IUPAC name
CAS number 463-58-1 Yes check.svgY
ChemSpider ID 9644
Molecular formula COS
Molar mass 60.07 g/mol
Density 2.51 g/L
Melting point

−138.8 °C (134 K)

Boiling point

−50.2 °C (223 K)

MSDS Carbonyl sulfide MSDS
EU Index Not listed
Related compounds
Related compounds Carbon dioxide
Carbon disulfide
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Carbonyl sulfide is the chemical 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 isoelectronic with it.

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

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.[3]




In the atmosphere

Carbonyl sulfide is the major sulfur compound naturally present in the atmosphere, at 0.5 (± 0.05) ppb, because it is emitted from volcanos and deep sea vents. As such it is a significant compound in the global sulfur cycle. Measurements on the Antarctica ice cores provide a detailed picture of OCS concentrations from 1640 to the present day separating anthropogenic and non-anthropogenic sulfur sources. Carbonyl sulfide is transported into the stratospheric sulfate layer where it is oxidized to sulfuric acid.

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, 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.

In foods

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.

In outer space

Carbonyl sulfide has been observed in interstellar medium.


Carbonyl sulfide is used as an intermediate in the production of thiocarbamate herbicides.[2] Carbonyl sulfide is a potential fumigant and a replacement for methyl bromide and phosphine.


It was first described in 1841,[4] 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 elemental sulfur. This reaction reverses above 1200 K. A laboratory synthesis entails the reaction potassium thiocyanate and sulfuric acid. The resulting gas contains significant amounts of byproducts and requires purification.[5]

KSCN + 2 H2SO4 + H2O → KHSO4 + NH4HSO4 + COS


As of 1994, there was limited information 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 (approximately 50 ppm for up to 12 weeks) does not affect the lungs or the heart.[2]


  1. ^ a b c d Hazardous Substances Data Bank (1994). MEDLARS Online Information Retrieval System, National Library of Medicine.
  2. ^ a b c d e f g Chemical Summary for Carbonyl sulfide, U.S. Environmental protection Agency.
  3. ^ Luke Leman, Leslie Orgel, M. Reza Ghadiri (2004). "Carbonyl Sulfide–Mediated Prebiotic Formation of Peptides". Science 306 (5694): 283–286. doi:10.1126/science.1102722. PMID 15472077.  
  4. ^ Couërbe, J. P. (1841). "Ueber den Schwefelkohlenstoff". Journal für Praktische Chemie 23: 83–124. doi:10.1002/prac.18410230105.  
  5. ^ Ferm R. J. (1957). "The Chemistry of Carbonyl sulfide". Chemical Reviews 57 (4): 621–640. doi:10.1021/cr50016a002.  

Further reading

  • Beck, M. T.; Kauffman, G. B. (1985). "COS and C3S2: The Discovery and Chemistry of Two Important Inorganic Sulfur Compounds". Polyhedron 4 (5): 775–781. doi:10.1016/S0277-5387(00)87025-4.  
  • Crutzen, P. (1976). "The possible importance of CSO for the sulfate layer of the stratosphere". Geophys. Res. Lett. 3: 73–76. doi:10.1029/GL003i002p00073.  
  • 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. doi:10.1021/ie020365n.  

External links


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