Carbon suboxide
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| Names | |
|---|---|
| IUPAC name
Propa-1,2-diene-1,3-dione
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| Identifiers | |
504-64-3  |
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| ChEBI | CHEBI:30086 |
| ChemSpider | 120106 |
| Jmol 3D model | Interactive image |
| MeSH | Carbon+suboxide |
| PubChem | 136332 |
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| Properties | |
| C3O2 | |
| Molar mass | 68.03 g·mol−1 |
| Appearance | colorless gas |
| Odor | strong, pungent odor |
| Density | 0.906 ± 0.06 g cm−3, gas at 298 K |
| Melting point | −111.3 °C (−168.3 °F; 161.8 K) |
| Boiling point | 6.8 °C (44.2 °F; 279.9 K) |
| reacts | |
| Solubility | soluble in 1,4-dioxane, ether, xylene, CS2, tetrahydrofuran |
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Refractive index (nD)
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1.4538 (6 °C) |
| 0 D | |
| Structure | |
| rhombic | |
| linear | |
| Thermochemistry | |
| 66.99 J/mol K | |
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Std molar
entropy (S |
276.1 J/mol K |
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Std enthalpy of
formation (ΔfH |
-93.6 kJ/mol |
| Related compounds | |
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Related oxides
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carbon dioxide carbon monoxide dicarbon monoxide |
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Related compounds
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carbon subsulfide carbon subnitride |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
Carbon suboxide, or tricarbon dioxide, is an oxide of carbon with chemical formula C3O2 or O=C=C=C=O. Its four cumulative double bonds make it a cumulene. It is one of the stable members of the series of linear oxocarbons O=Cn=O, which also includes carbon dioxide (CO2) and pentacarbon dioxide (C5O2).
The substance was discovered in 1873 by Benjamin Brodie by subjecting carbon monoxide to an electric current. He claimed that the product was part of a series of "oxycarbons" with formulas Cx+1Ox, namely C, C2O, C3O2, C4O3, C5O4, ..., and to have identified the last two;[1][2] however only C3O2 is known. In 1891 Marcellin Berthelot observed that heating pure carbon monoxide at about 550 °C created small amounts of carbon dioxide but no trace of carbon, and assumed that a carbon-rich oxide was created instead, which he named "sub-oxide". He assumed it was the same product obtained by electric discharge and proposed the formula C2O.[3] Otto Diels later stated that the more organic names dicarbonyl methane and dioxallene were also correct.
It is commonly described as an oily liquid or gas at room temperature with an extremely noxious odor.[4]
Synthesis
It is synthesized by warming a dry mixture of phosphorus pentoxide (P4O10) and malonic acid or the esters of malonic acid.[5] Therefore, it can be also considered as the anhydride of malonic anhydride, i.e. the "second anhydride" of malonic acid. Malonic anhydride (not to be confused with maleic anhydride) is a real molecule.[6]
Several other ways for synthesis and reactions of carbon suboxide can be found in a review from 1930 by Reyerson.[7]
Carbon suboxide polymerizes spontaneously to a red, yellow, or black solid. The structure is postulated to be poly(α-pyronic), similar to the structure in 2-pyrone (α-pyrone).[8][9] In 1969, it was hypothesized that the color of the Martian surface was caused by this compound; this was disproved by the Viking Mars probes (the red color is instead due to iron oxide.)[10]
Uses
Carbon suboxide is used in the preparation of malonates; and as an auxiliary to improve the dye affinity of furs.
Biological role
Carbon suboxide, C3O2, can be produced in small amounts in any biochemical process that normally produces carbon monoxide, CO, for example, during heme oxidation by heme oxygenase-1. It can also be formed from malonic acid. It has been shown that carbon suboxide in an organism can quickly polymerize into macrocyclic polycarbon structures with the common formula (C3O2)n (mostly (C3O2)6 and (C3O2)8), and that those macrocyclic compounds are potent inhibitors of Na+/K+-ATP-ase and Ca-dependent ATP-ase, and have digoxin-like physiological properties and natriuretic and antihypertensive actions. Those macrocyclic carbon suboxide polymer compounds are thought to be endogenous digoxin-like regulators of Na+/K+-ATP-ases and Ca-dependent ATP-ases, and endogenous natriuretics and antihypertensives.[11][12][13] Other than that, some authors think also that those macrocyclic compounds of carbon suboxide can possibly diminish free radical formation and oxidative stress and play a role in endogenous anticancer protective mechanisms, for example in the retina.[14]
References
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