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| Names | |
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| IUPAC names | |
| Systematic IUPAC name Thioxomethanone | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
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| ECHA InfoCard | 100.006.674 |
| EC Number |
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| KEGG |
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| UNII | |
| UN number | 2204 |
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| Properties | |
| 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; 134.3 K) |
| Boiling point | −50.2 °C (−58.4 °F; 223.0 K) |
| Critical point (T,P) | 101.85 °C (215.3 °F; 375.0 K), 58.03 standard atmospheres (5,879.9 kPa; 852.8 psi)[2] |
| 0.376 g/100 mL (0 °C) 0.125 g/100 mL (25 °C) | |
| Solubility | very soluble inKOH,CS2 soluble inalcohol,toluene |
| −32.4×10−6 cm3/mol | |
| 0.65 D | |
| Thermochemistry | |
| 41.5 J/(mol⋅K) | |
Std molar entropy(S⦵298) | 231.5 J/(mol⋅K) |
Std enthalpy of formation(ΔfH⦵298) | −141.8 kJ/mol |
| Hazards | |
| GHS labelling: | |
   | |
| Danger | |
| H220,H315,H319,H331,H335 | |
| P210,P261,P264,P271,P280,P302+P352,P304+P340,P305+P351+P338,P311,P312,P321,P332+P313,P337+P313,P362,P377,P381,P403,P403+P233,P405,P410+P403,P501 | |
| NFPA 704 (fire diamond) | |
| Explosive limits | 12–29% |
| Safety data sheet (SDS) | Carbonyl sulfide MSDS |
| Related compounds | |
Related compounds | Carbon dioxide Carbon disulfide Carbonyl selenide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Carbonyl sulfide is thechemical compound with thelinear formulaO=C=S. It is a colorless flammablegas with an unpleasantodor. It is a linear molecule consisting of acarbonyldouble bonded to a sulfur atom. Carbonyl sulfide can be considered to be intermediate betweencarbon dioxide andcarbon disulfide, both of which arevalence isoelectronic with it.
Carbonyl sulfide is the most abundant sulfur compound naturally present in the atmosphere, at0.5±0.05 ppb, because it is emitted from oceans,volcanoes anddeep sea vents. As such, it is a significant compound in the globalsulfur cycle. Measurements on theAntarcticaice 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 ofanthropogenic and non-anthropogenic sources of this gas to the atmosphere.[3] Some carbonyl sulfide that is transported into thestratospheric sulfate layer is oxidized to sulfuric acid.[4] Sulfuric acid forms particulate which affectsenergy balance due tolight scattering.[5] The long atmospheric lifetime of COS makes it the major source of stratospheric sulfate, thoughsulfur dioxide from volcanic activity can be significant too.[5] 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.[6][7][8] 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 theirtire wear,[9] coal-fired power plants,coking ovens,biomass combustion, fish processing, combustion of refuse and plastics, petroleum manufacture, and manufacture of synthetic fibers, starch, and rubber.[10] The average total worldwide release of carbonyl sulfide to the atmosphere has been estimated[when?] at about 3 million tons per year, of which less than one third was related to human activity.[10] It is also a significant sulfur-containing impurity in manyfuel gases such assynthesis gas, which are produced from sulfur-containing feedstocks.[11]
Carbonyl sulfide is present infoodstuffs, such ascheese and preparedvegetables of thecabbage family. Traces of COS are naturally present ingrains andseeds in the range of 0.05–0.1 mg/kg.
Carbonyl sulfide has been observed in theinterstellar medium (see alsoList of molecules in interstellar space), incomet 67P[12] and in theatmosphere of Venus, where, because of the difficulty of producing COS inorganically, it is considered a possible indicator of life.[13]
Carbonyl sulfide is used as an intermediate in the production of thiocarbamate herbicides.[14]
The hydrolysis of carbonyl sulfide is promoted by chromium-based catalysts:[11]
This conversion is catalyzed in solution bycarbonic anhydrase enzymes in plants and mammals. Because of this chemistry, the release of carbonyl sulfide from small organic molecules has been identified as a strategy for delivering hydrogen sulfide, which isgaseous signaling molecule.[15][16]
This compound is found tocatalyze the formation ofpeptides fromamino acids. This finding is an extension of theMiller–Urey experiment, and it is suggested that carbonyl sulfide played a significant role in theorigin of life.[17]
In ecosystem science,[18] are increasingly being used to describe the rate ofphotosynthesis.[19][20]
Carbonyl sulfide was first described in 1841,[21] but was apparently mischaracterized as a mixture of carbon dioxide andhydrogen sulfide.Carl von Than first characterized the substance in 1867. It forms whencarbon monoxide reacts with molten sulfur:
This reaction reverses above 1200 K (930 °C; 1700 °F).
A laboratory synthesis entails the reactionpotassium thiocyanate andsulfuric acid:
The resulting gas contains significant amounts of byproducts and requires purification.[22]
Hydrolysis ofisothiocyanates inhydrochloric acid solution also affords COS.
Carbonyl sulfide has the "rotten egg" odor characteristic of sulfides, although some sources suggest that the associated odor is due to impurities, and not present in the pure compound.[23] The detectability threshold is estimated at 135μg/m.[23]
As of 1994, limited information existed on the acute toxicity of carbonyl sulfide in humans and in animals.[14] High concentrations (above 1000 ppm) can cause sudden collapse, convulsions, and death from respiratory paralysis.[10][14] Occasional fatalities have been reported, practically without local irritation or olfactory warning.[14] In tests with rats, 50% animals died when exposed to1400 ppm of COS for 90 minutes, or at3000 ppm for 9 minutes.[14] Limited studies with laboratory animals also suggest that continued inhalation of low concentrations (around 50 ppm for up to 12 weeks) does not affect the lungs or the heart.[14]
Carbonyl sulfide is a potential alternativefumigant[24] tomethyl bromide andphosphine. In some cases, however, residues on the grain result in flavours that are unacceptable to consumers, such as in barley used for brewing.
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