From Wikipedia, the free encyclopedia

Carbon suboxide
IUPAC name	propa-1,2-diene-1,3-dione
Identifiers
CAS number	504-64-3
PubChem	136332
ChEBI	30086
SMILES	O=C=C=C=O
InChI	1/C3O2/c4-2-1-3-5
Properties
Molecular formula	C3O2
Molar mass	68.0309 g mol−1
Appearance	colorless gas strong, pungent odor
Density	0.906 ± 0.06 g/cm3, gas at 298 K
Melting point	−111.3 °C
Boiling point	6.8 °C
Refractive index (nD)	1.4538 (0 °C)
Structure
Molecular shape	linear
Related compounds
Related oxides	carbon dioxide carbon monoxide dicarbon monoxide carbon trioxide
Related compounds	carbon subnitride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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=C_n=O, which also includes carbon dioxide (CO₂) and pentacarbon dioxide (C₅O₂).

Brodie discovered it in 1873 by submitting electric current to carbon monoxide.^[1][2] Marcellin Berthelot created the name carbon suboxide, ^[3] while Otto Diels later stated that the more organic names dicarbonyl methane and dioxallene were also correct.

It is most commonly described as an evil-smelling gas.

Synthesis

It is synthesized by warming a dry mixture of phosphorus pentoxide (P₄O₁₀) and malonic acid or the esters of malonic acid.^[4] 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.^[5]

Several other ways for synthesis and reactions of carbon suboxide can be found in a review from 1930 by Reyerson.^[6]

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). ^[7][8] In 1969, it was hypothesized that the color of Martian surface was caused by this compound; this was disproved by the Viking Mars probes.^[9]

Uses

Carbon suboxide is used in the preparation of malonates; and as an auxiliary to improve the dye affinity of furs.

See also

• Carbon subsulfide, C₃S₂, whose structure is S=C=C=C=S
• Carbon monoxide (CO)
• Dicarbon monoxide (C₂O)
• Dicarbon dioxide (C₂O₂)

References

External links

• WebElements page on compound's properties