Carbon dioxide suboxide

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Tricarbon dioxide, C3O2, often called carbon suboxide and ponderously referred to in Chemical Abstracts as l,2-propadiene-l,3-dione, is a foul-smelling gas obtained by dehydrating malonic acid, CH2(C02H)2, at... 

The dehydration of malonic acid, H02C-CH2-C02H, produces C302 (known as tricarbon dioxide or carbon suboxide). Draw the structure for C302 and describe the bonding in terms of resonance structures. 

Although it is stable at low temperatures, carbon suboxide will readily bum, and it polymerizes when heated. Pentacarbon dioxide, C502, has been prepared, but like C302 it has no important uses. 

The decompositions of C302, CO, C02, CS2, COS, CSe2 and COSe are dealt with in this section. Apart from carbon suboxide, this is a group of stable, un-reactive compounds. Considerable emphasis has been placed on the investigation of the photolytic decompositions of some of these compounds which are thought to provide useful sources of atoms (C, O, S and Se) and free radicals (C20). The photochemistry of carbon dioxide has particular relevance to the chemistry of planetary atmospheres, although to date the mechanism of C02 photolysis remains obscure. 

Carbon Oxides. Sec also Carbon Dioxide Carbon Monoxide and Carbon Suboxide... 

CARBON SUBOXIDE. Cy02, formula weight 68.03, colorless, toxic, gas at room temperature, very unpleasant odor, sp gr 2.10 (air = 1.00). 1.24 (liquid at -87°C). mp — I07 C. bp 7°C (760 lorr). bums with a blue smoky Haute, producing CO . When condensed to liquid, the oxide slowly changes at ordinary temperature to a dark red solid, soluble in water to a red solution. Reacts with water to form malonic acid, with hydrogen chloride to form malonyl chloride, with ammonia to form malonamide. Made by heating malonic acid or its ester at 300°C under diminished pressure, and separation from simultaneously formed carbon dioxide and ethylene by condensation and fractional distillation. 

In addition to carbon monoxide (CO) and carbon dioxide (C02), there is a third compound of carbon and oxygen called carbon suboxide. If a 2.500 g sample of carbon suboxide contains 1.32 g of C and 1.18 g of O, show that the law of multiple proportions is followed. 

The element carbon forms three compounds with oxygen, the most common being the dioxide (C02). The others are the very poisonous carbon monoxide (CO) and the relatively less well known carbon suboxide... 

Carbonic Acid.—Berthelot1 observed the decomposition into carbon monoxide and oxygen. The reaction is reversible, an equilibrium occurs, in which, however, the partially ozonized oxygen converts carbon monoxide into carbonic acid and a solid carbon suboxide, C4O3, which Brodie 2 had already formerly observed. Carbon dioxide, under a pressure of 3-10 mm. mercury, splits up very rapidly and up to 70 per cent, into carbon monoxide and oxygen (Norman Collie 3). 

Carbon suboxide, C302, contains carbon in the formal oxidation state of +4/3. Because this is lower than its oxidation state in CO or C02, the oxide is called carbon suboxide. It could also be named as tricarbon dioxide. The linear structure of the molecule is... 

Carbon monoxide and carbon dioxide cannot be polymerized. However, they can be copolymerized with some monomers. The same is true of sulphur dioxide. Carbon suboxide can be polymerized under certain conditions [62]. 

Ethylenedione. the dimer of carbon monoxide, has attracted chemists interest since at least 1913 when its synthesis by dechlorination of oxalyl chloride was unsuccessfully attempted 37). This substance, which lies between carbon dioxide and carbon suboxide in the series of oxycumulenes, is the simplest possible unsaturated diketone. It can be represented by a number of canonical structures as shown below ... 

The three most stable oxides of carbon are carbon monoxide (CO), carbon-dioxide (C02), and carbon suboxide (C302). The space-filling models for these three compounds are... 

For example, Faltings, Groth, and Harteck o found that carbon monoxide could be decomposed by the action of xenon resonance radiation at 1,295A, with the production of carbon dioxide and carbon suboxide. No reaction took place with radiation of wavelength 1,470A. From this it was concluded that Z)(GO) <9 57 eV. 

Reaction (7) proceeds at room temperature and at one atmosphere pressure of carbon dioxide, thus converting the bridging ketenylidene ligand into the bridging oxided The ketenylidene complex reacts with carbon dioxide even in the solid state the gas produced from the zirconium derivative, promptly evacuated into a mass-spectrometer, was shown to be carbon suboxide C302d The inorganic reaction product appears to catalyze the polymerization of carbon suboxide to red solid productsd The structure of the product resulting from reaction (7), R = Pr , is shown in Fig. 8b. 

Under the natural conditions of weathering, slow oxidation of coal occtrrs with the formation of carbon suboxide and no, or very little, carbon dioxide is generated (Davidson, 1990). The heat release accompar ing coal oxidation to the polymerized substance can be described as... 

Carbon C3 Carbon suboxide —> Tricarbon dioxide C—c 1.277 linear uv... 

It is interesting to note that a formal pattern for the resonance positions similar to that of allene (11) and pentatetraene (222) is also found for carbon dioxide (204) and carbon suboxide (240) (130). 

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