Carbon suboxide

Carbon suboxide, or tricarbon dioxide, is an oxide of carbon with chemical formula C
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 (C
). Although if carefully purified it can exist at room temperature in the dark without decomposing, it will polymerize under certain conditions.

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 C2O, C
, C4O3, C
, ..., and to have identified the last two;[3][4] however only C
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 C
.[5] Otto Diels later stated that the more organic names dicarbonylmethane and dioxallene were also correct.

It is commonly described as an oily liquid or gas at room temperature with an extremely noxious odor.[6]

Carbon suboxide
Stick model of carbon suboxide
Spacefill model of carbon suboxide
IUPAC name
3D model (JSmol)
MeSH Carbon+suboxide
Molar mass 68.031 g·mol−1
Appearance colorless gas
Odor strong, pungent odor
Density 3.0 kg/m3, gas[1]

1.114 g/cm3, liquid[2]

Melting point −111.3 °C (−168.3 °F; 161.8 K)
Boiling point 6.8 °C (44.2 °F; 279.9 K)
Solubility soluble in 1,4-dioxane, ether, xylene, CS2, tetrahydrofuran
1.4538 (6 °C)
0 D
quasilinear (phase dependent)
66.99 J/mol K
276.1 J/mol K
-93.6 kJ/mol
Related compounds
Related oxides
carbon dioxide
carbon monoxide
dicarbon monoxide
Related compounds
carbon subsulfide
carbon subnitride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).


It is synthesized by warming a dry mixture of phosphorus pentoxide (P
) and malonic acid or its esters.[7] Therefore, it can be also considered as the anhydride of malonic anhydride, i.e. the "second anhydride" of malonic acid.[8]

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).[9][10] The number of monomers in the polymers is variable (see Oxocarbon#Polymeric carbon oxides). 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).[11]


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

Biological role

Carbon suboxide macrocyclic polymers
Those are 6- or 8-ring macrocyclic polymers of carbon suboxide that were found in living organisms. They are acting as an endogenous digoxin-like Na+/K+-ATP-ase and Ca-dependent ATP-ase inhibitors, endogenous natriuretics, antioxidants and antihypertensives

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 (C
)n (mostly (C
and (C
), 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.[12][13][14] 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.[15]

Structure and bonding

The structure of carbon suboxide has been the subject of experiments and computations since the 1970s. The central issue is the question of whether the molecule is linear or bent (i.e., whether ). Studies general agree that the molecule is highly non-rigid, with a very shallow barrier to bending. According to one study, the molecular geometry is described by a double-well potential with a minimum at θC2 ~ 160°, an inversion barrier of 20 cm−1 (0.057 kcal/mol), and a total energy change of 80 cm−1 (0.23 kcal/mol) for 140° ≤ θC2 ≤ 180°.[16] The small energetic barrier to bending is around the same order of magnitude as the vibrational zero-point energy. Therefore, the molecule is best described as quasilinear. While infrared[17] and electron diffraction[18] studies have indicated that C
has a bent structure in the gas phase, the compound was found to possess at least an average linear geometry in the solid phase by X-ray crystallography, although the large thermal ellipsoids of the oxygen atoms and C2 have been interpreted to be consistent with rapid bending (minimum θC2 ~ 170°), even in the solid state.[19]

A heterocumulene resonance form of carbon suboxide based on minimization of formal charges does not readily explain the molecule's non-rigidity and deviation from linearity. To account for the quasilinear structure of carbon suboxide, Frenking has proposed that carbon suboxide be regarded as a "coordination complex" of carbon(0) bearing two carbonyl ligands and two lone pairs: .[20] However, the contribution of dative bonding in C
and similar species has been criticized as chemically unreasonable by others.[21]

Carbon suboxide dative


  1. ^ "Carbon Suboxide". WebElements Periodic Table. Retrieved 19 Feb 2019.
  2. ^ Weast RC, Astle MJ, eds. (1983). CRC Handbook of Chemistry and Physics (64th ed.). Boca Raton: CRC Press. p. B-82. ISBN 9780849304637.
  3. ^ Brodie BC (1873). "Note on the Synthesis of Marsh-Gas and Formic Acid, and on the Electric Decomposition of Carbonic Oxide". Proc. Royal Soc. Lond. 21 (139–147): 245–247. doi:10.1098/rspl.1872.0052. JSTOR 113037. When pure and dry carbonic oxide [=carbon monoxide] is circulated through the induction-tube, and there submitted to the action of electricity, a decomposition of the gas occurs [...] Carbonic acid [=carbon dioxide] is formed, and simultaneously with its formation a solid deposit may be observed in the induction-tube. This deposit appears as a transparent film of a red-brown color, lining the walls of the tube. It is perfectly soluble in water, which is strongly colored by it. The solution has an intensely acid reaction. The solid deposit, in the dry condition before it has been in contact with the water, is an oxide of carbon.
  4. ^ Brodie BC (1873). "Ueber eine Synthese von Sumpfgas und Ameisensäure und die electrische Zersetzung des Kohlenoxyds". Liebigs Ann. 169 (1–2): 270–271. doi:10.1002/jlac.18731690119.
  5. ^ Berthelot M (1891). "Action de la chaleur sur l'oxyde de carbone". Annales de Chimie et de Physique. 6 (24): 126–132. Archived from the original on 17 Feb 2012. Retrieved 21 Feb 2007.
  6. ^ a b Reyerson LH, Kobe K (1930). "Carbon Suboxide". Chem. Rev. 7 (4): 479–492. doi:10.1021/cr60028a002.
  7. ^ Diels O, Wolf B (1906). "Ueber das Kohlensuboxyd. I" (PDF). Chem. Ber. 39: 689–697. doi:10.1002/cber.190603901103.
  8. ^ Perks HM, Liebman JF (2000). "Paradigms and Paradoxes: Aspects of the Energetics of Carboxylic Acids and Their Anhydrides". Structural Chemistry. 11 (4): 265–269. doi:10.1023/A:1009270411806.
  9. ^ Ballauff M, Li L, Rosenfeldt S, et al. (2004). "Analysis of Poly(carbon suboxide) by Small-Angle X-ray Scattering". Angewandte Chemie International Edition. 43 (43): 5843–5846. doi:10.1002/anie.200460263. PMID 15523711.
  10. ^ Ellern A, Drews T, Seppelt K (2001). "The Structure of Carbon Suboxide, C
    , in the Solid State". Z. Anorg. Allg. Chem. 627 (1): 73–76. doi:10.1002/1521-3749(200101)627:1<73::AID-ZAAC73>3.0.CO;2-A.
  11. ^ Plummer WT, Carsont RK (1969). "Mars: Is the Surface Colored by Carbon Suboxide?". Science. 166 (3909): 1141–1142. doi:10.1126/science.166.3909.1141. PMID 17775571.
  12. ^ Kerek F (2000). "The structure of the digitalislike and natriuretic factors identified as macrocyclic derivatives of the inorganic carbon suboxide". Hypertension Research. 23 (Suppl S33): S33–38. doi:10.1291/hypres.23.Supplement_S33. PMID 11016817.
  13. ^ Stimac R, Kerek F, Apell HJ (2003). "Macrocyclic carbon suboxide oligomers as potent inhibitors of the Na,K-ATPase". Ann. N. Y. Acad. Sci. 986: 327–329. doi:10.1111/j.1749-6632.2003.tb07204.x. PMID 12763840.
  14. ^ Kerek F, Stimac R, Apell HJ, et al. (2002). "Characterization of the macrocyclic carbon suboxide factors as potent Na,K-ATPase and SR Ca-ATPase inhibitors". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1567 (1–2): 213–220. doi:10.1016/S0005-2736(02)00609-0. PMID 12488055.
  15. ^ Tubaro E (1966). "Carbon suboxide, the probable precursor of an antitumor cellular substance: retina". Bollettino Chimico Farmaceutico (in Italian). 105 (6): 415–416. PMID 6005012.
  16. ^ Brown RD (1993). "Structural Information on Large Amplitude Motions". In Laane J, Dakkouri M, Veken Bv, et al. (eds.). Structures and Conformations of Non-Rigid Molecules. NATO ASI Series. 410. Springer Netherlands. pp. 99–112. doi:10.1007/978-94-011-2074-6_5. ISBN 9789401049207.
  17. ^ Jensen P, Johns JW (1986). "The infrared spectrum of carbon suboxide in the ν6 fundamental region: Experimental observation and semirigid bender analysis". J. Mol. Spectrosc. 118 (1): 248–266. doi:10.1016/0022-2852(86)90239-0.
  18. ^ Clark A (1970). "The potential function for the CCC bending in carbon suboxide". Chem. Phys. Lett. 6 (5): 452–456. doi:10.1016/0009-2614(70)85190-9.
  19. ^ Ellern A, Drews T, Seppelt K (2001). "The Structure of Carbon Suboxide, C
    , in the Solid State". Z. Anorg. Allg. Chem. 627 (1): 73–76. doi:10.1002/1521-3749(200101)627:1<73::aid-zaac73>;2-a. ISSN 1521-3749.
  20. ^ Frenking G, Tonner R (2009). "Divalent carbon(0) compounds". Pure Appl. Chem. 81 (4): 597–614. doi:10.1351/pac-con-08-11-03. ISSN 1365-3075.
  21. ^ Himmel D, Krossing I, Schnepf A (2014). "Dative Bonds in Main-Group Compounds: A Case for Fewer Arrows!". Angewandte Chemie International Edition. 53 (2): 370–374. doi:10.1002/anie.201300461. ISSN 1521-3773.

External links

A.J. Drexel Plasma Institute

The Drexel Plasma Institute, in Camden, New Jersey, is the largest university-based plasma research facility in the United States of America. Led by Drexel University, the members of the scientific team are from University of Illinois at Chicago, Argonne National Laboratory, Pacific Northwest National Laboratory and Kurchatov Institute of Atomic Energy. The primary fields of research are applications in medicine, Environmental Control, energy, and agricultural industries. The institute actively develops and researches specific types of plasma discharges such as gliding arc, dielectric barrier discharge, gliding arc tornado, reverse vortex flow, Pulsed Corona Discharge, and many more.

Atomic carbon

Atomic carbon, systematically named carbon and λ0-methane, also called monocarbon, is colourless gaseous inorganic chemical with the chemical formula C (also written [C]). It is kinetically unstable at ambient temperature and pressure, being removed through autopolymerisation.

Atomic carbon is the simplest form of carbon, and is also the progenitor of carbon clusters. In addition, it may be considered to be the graphite monomer.

Bis(triphenylphosphine)iminium chloride

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [(C6H5)3P)2N]Cl, often written [(Ph3P)2N]Cl and abbreviated PPNCl. This colorless salt is a source of the PPN+ cation, which is used to isolate reactive anions. PPN+ is a phosphazene.


Carbon (from Latin: carbo "coal") is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.The atoms of carbon can bond together in different ways, termed allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require high temperature to react even with oxygen.

The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates. Carbon forms a vast number of compounds, more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. For this reason, carbon has often been referred to as the "king of the elements".

Carbon subsulfide

Carbon subsulfide is an inorganic chemical compound with the formula C3S2. This deep red liquid is immiscible with water but soluble in organic solvents. It readily polymerizes at room temperature to form a hard black solid.

Compounds of carbon

Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings.

Coordinate covalent bond

A coordinate covalent bond, also known as a dative bond or coordinate bond is a kind of 2-center, 2-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal ions to ligands involves this kind of interaction. This type of interaction is central to Lewis theory.


A cumulene is a hydrocarbon with three or more cumulative (consecutive) double bonds. They are analogous to allenes, only having a more extensive chain. The simplest molecule in this class is butatriene (H2C=C=C=CH2), which is also called simply cumulene. Unlike most alkanes and alkenes, cumulenes tend to be rigid, comparable to alkynes, which makes them appealing for molecular nanotechnology. Polyynes are another kind of rigid carbon chains. Cumulenes are found in regions of outer space where hydrogen is rare (see astrochemistry). Cumulenes containing heteroatoms are called heterocumulenes; an example is carbon suboxide.

Dicarbon monoxide

Dicarbon monoxide (C2O) is a molecule that contains two carbon atoms and one oxygen atom. It is a linear molecule that, because of its simplicity, is of interest in a variety of areas. It is, however, so extremely reactive that it is not encountered in everyday life. It is classified as a cumulene and an oxocarbon.


Dicyanoacetylene, also called carbon subnitride or but-2-ynedinitrile (IUPAC), is a compound of carbon and nitrogen with chemical formula C4N2. It has a linear molecular structure, N≡C−C≡C−C≡N (often abbreviated as NC4N), with alternating triple and single covalent bonds. It can be viewed as acetylene with the two hydrogen atoms replaced by cyanide groups.

At room temperature, dicyanoacetylene is a clear liquid. Because of its high endothermic heat of formation, it can explode to carbon powder and nitrogen gas, and it burns in oxygen with a bright blue-white flame at a temperature of 5260 K (4990 °C, 9010 °F), the hottest flame in oxygen; burnt in ozone the flame temperature exceeds 6000 K .

Gaseous signaling molecules

Gaseous signaling molecules are gaseous molecules that are either synthesised internally (endogenously) in the organism, tissue or cell or are received by the organism, tissue or cell from outside (say, from the atmosphere or hydrosphere, as in the case of oxygen) and that are used to transmit chemical signals which induce certain physiological or biochemical changes in the organism, tissue or cell. The term is applied to, for example, oxygen, carbon dioxide, nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrous oxide, hydrogen cyanide, ammonia, methane, hydrogen, ethylene, etc.

Many, but not all, gaseous signaling molecules are called gasotransmitters.

The biological roles of each of the gaseous signaling molecules are in short outlined below.

List of compounds with carbon number 3

This is a partial list of molecules that contain 3 carbon atoms.

Malonic anhydride

Malonic anhydride or oxetane-2,4-dione is an organic compound with chemical formula C3H2O3 or CH2(CO)2O. It can be viewed as the anhydride of malonic acid, or a double ketone of oxetane.

Malonic anhydride was first synthesized in 1988 by ozonolysis of diketene. Some derivatives, such as 3,3-dimethyl-oxetane-2,4-dione, are known.


An oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen.The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide (CO2) with IUPAC names carbon(II) oxide and carbon(IV) oxide respectively. Many other stable (practically if not thermodynamically) or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide (C3O2 or O=C=C=C=O) and mellitic anhydride (C12O9).

While textbooks will often list only the first three, and rarely the fourth, a large number of other oxides are known today, most of them synthesized since the 1960s. Some of these new oxides are stable at room temperature. Some are metastable or stable only at very low temperatures, but decompose to simpler oxocarbons when warmed. Many are inherently unstable and can be observed only momentarily as intermediates in chemical reactions or are so reactive that they can exist only in the gas phase or under matrix isolation conditions.

The inventory of oxocarbons appears to be steadily growing. The existence of graphene oxide and of other stable polymeric carbon oxides with unbounded molecular structures suggests that many more remain to be discovered.


Polycarbonyl, (also known as polymeric-CO, p-CO or poly-CO) is a solid metastable and explosive polymer of carbon monoxide. The polymer is produced by exposing carbon monoxide to high pressures. The structure of the solid appears amorphous, but may include a zig zag of equally spaced CO groups.


Propadienone is an organic compound with molecular formula C3H2O consisting of a Propadiene carbon framework with a ketone functional group. Structure of propadienone is not the same as propadiene of Carbon suboxide. In propadienone, Oxygen has +1 formal charge and C2 caron has -1 formal charge.


Suboxides are a class of oxides wherein the electropositive element is in excess relative to the “normal” oxides. When the electropositive element is a metal, the compounds are sometimes referred to as “metal-rich”. Thus the normal oxide of caesium is Cs2O, which is described as a Cs+ salt of O2−. A suboxide of caesium is Cs11O3, where the charge on Cs is clearly less than 1+, but the oxide is still described as O2−. Suboxides typically feature extensive bonding between the electropositive element, often leading to clusters.

Examples of suboxides include

Carbon suboxide, C3O2;

Boron suboxide, B6O;

Rubidium suboxide, Rb9O2;

Silicon suboxide, SiOx (x < 2)

Tetracarbon dioxide

Tetracarbon dioxide is an oxide of carbon, a chemical compound of carbon and oxygen, with chemical formula C4O2 or O=C=C=C=C=O. It can be regarded as butatriene dione, the double ketone of butatriene — more precisely 1,2,3-butatriene-1,4-dione.Butatriene dione is the fourth member of the family of linear carbon dioxides O(=C)n=O, that includes carbon dioxide CO2 or O=C=O, ethylene dione C2O2 or O=C=C=O, carbon suboxide C3O2 or O=C=C=C=O, pentacarbon dioxide C5O2 or O=C=C=C=C=C=O, and so on.

The compound was obtained in 1990 by Maier and others, by flash vacuum pyrolysis of cyclic azaketones in a frozen argon matrix. It was also obtained in the same year by Sülzle and Schwartz through impact ionization of ((CH3-)2(C4O2)(=O)2=)2 in the gas phase. Although theoretical studies indicated that the even-numbered members of the O(=C)n=O family should be inherently unstable, C4O2 is indefinitely stable in the matrix, but is decomposed by light into tricarbon monoxide C3O and carbon monoxide CO. It has a triplet ground state.

Tricarbon monoxide

Tricarbon monoxide C3O is a reactive radical oxocarbon molecule found in space, and which can be made as a transient substance in the laboratory. It can be trapped in an inert gas matrix or made as a short lived gas. C3O can be classified as a ketene or an oxocumulene a kind of heterocumulene.

Common oxides
Exotic oxides
Compounds derived from oxides
Carbon ions
Oxides and related
Mixed oxidation states
+1 oxidation state
+2 oxidation state
+3 oxidation state
+4 oxidation state
+5 oxidation state
+6 oxidation state
+7 oxidation state
+8 oxidation state


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