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Carbon suboxide

Carbon suboxide

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Encyclopedia
Carbon suboxide, or tricarbon dioxide, is an oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

 of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C3O2 or O=C=C=C=O. Its four cumulative double bonds make it a cumulene
Cumulene
A cumulene is a chemical compound with two or more cumulative double bonds, for example butatriene , H2C=C=C=CH2. Unlike alkanes and most alkenes, cumulenes tend to be rigid, which makes them appealing for molecular nanotechnology. Polyynes are another kind of rigid carbon chains...

. It is one of the stable members of the series of linear oxocarbon
Oxocarbon
An oxocarbon or oxide of carbon is an inorganic compound consisting only of carbon and oxygen.The simplest and most common oxocarbons are carbon monoxide and carbon dioxide...

s O=Cn=O, which also includes carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (CO2) and pentacarbon dioxide
Pentacarbon dioxide
Pentacarbon dioxide, officially penta-1,2,3,4-tetraene-1,5-dione, is an oxide of carbon with formula C5O2 or O=C=C=C=C=C=O....

 (C5O2).

The substance was discovered in 1873 by Benjamin Brodie
Sir Benjamin Collins Brodie, 2nd Baronet
Sir Benjamin Collins Brodie, 2nd Baronet FRS was an English chemist.Brodie was the son of Sir Benjamin Collins Brodie, 1st Baronet, and his wife Anne , and was educated at Harrow and Balliol College, Oxford...

 by submitting carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 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; however only C3O2 is known. In 1891 Marcellin Berthelot
Marcellin Berthelot
Marcelin Pierre Eugène Berthelot was a French chemist and politician noted for the Thomsen-Berthelot principle of thermochemistry. He synthesized many organic compounds from inorganic substances and disproved the theory of vitalism. He is considered as one of the greatest chemists of all time.He...

 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 discharged and proposed the formula C2O. Otto Diels
Otto Diels
Otto Paul Hermann Diels was a German chemist. He was the son of a professor of philology at the University of Berlin, where he himself earned his doctorate in chemistry, in the group of Emil Fischer....

 later stated that the more organic names dicarbonyl methane and dioxallene were also correct.

It is commonly described as a oily liquid or gas at room temperature with an extremely noxious odor.

Synthesis


It is synthesized by warming a dry mixture of phosphorus pentoxide
Phosphorus pentoxide
Phosphorus pentoxide is a chemical compound with molecular formula P4O10 . This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant.-Structure:...

 (P4O10) and malonic acid
Malonic acid
Malonic acid is a dicarboxylic acid with structure CH22. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester...

 or the ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s of malonic acid
Malonic acid
Malonic acid is a dicarboxylic acid with structure CH22. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester...

.
Therefore, it can be also considered as the anhydride of malonic anhydride
Malonic anhydride
Malonic anhydride or oxetane-2,4-dione is an organic compound with chemical formula C3H2O3 or CH22O. It can be viewed as the anhydride of malonic acid, or a double ketone of oxetane....

, i.e. the "second anhydride" of malonic acid
Malonic acid
Malonic acid is a dicarboxylic acid with structure CH22. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester...

. Malonic anhydride (not to be confused with maleic anhydride
Maleic anhydride
Maleic anhydride is an organic compound with the formula C2H22O. It is the acid anhydride of maleic acid and in its pure state it is a colourless or white solid with an acrid odour....

) is a real molecule.

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

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
2-Pyrone
2-Pyrone is an unsaturated cyclic chemical compound with the molecular formula C5H4O2. It is isomeric with 4-pyrone....

 (α-pyrone).

In 1969, it was hypothesized that the color of Martian surface was caused by this compound; this was disproved by the Viking Mars probes
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...

.

Uses


Carbon suboxide is used in the preparation of malonate
Malonate
The malonate or propanedioate ion is CH222− . Malonate compounds include salts and esters of malonic acid, such as*diethyl malonate, 2,*dimethyl malonate, 2,...

s; and as an auxiliary to improve the dye affinity of furs.

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