504-64-3 carbon suboxide

Carbon suboxide, C3O2, OCCCO. M.p. — 107 C, b.p. 6-8°C. A toxic gas (malonic acid plus P2O5) which polymerizes at room temperature. Reforms malonic acid with water. 

Liquid carbon suboxide added to a solution of 2-ethylaminothiarole in anhydrous ether at 0°C gives immediate formation of a white precipitate of the mesoionic xanthine (121) (R=H) (130), otherwise prepared by reaction between 2-ethylaminothiazole and phenoxycarbonyl isocyanate (see p. 65 and Ref. 304),... 

Ketenes and related compounds have been reviewed extensively (1 9). For the synthesis and synthetic uses of conjugated ketenes see Reference 10. Ketenes with three or more cumulated double bonds have been prepared (11,12). The best known is carbon suboxide [504-64-3] 3 2 preparative uses and has been reviewed (13—16). Thioketenes (17,18), ketenimines (19—21), and their dimers show interesting reactivity, but they have not achieved iadustrial importance to date. 

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. 

Figure 3-14 shows an induction period in the reaction of carbon suboxide (O=C=C=C=0) with triethylamine. This reaction is complex and is not yet... 

Figure 3-14. Absorbance-time plots for the reaction of carbon suboxide and triethylamine in ether solution in the presence of acetic anhydride. The initial C3O2 concentration was 2.03 X I0 - M the amine concentrations were 3 X lO " M, 5 x 10 M, and 7 X lO " M.

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... 

Malonic acid has been made by the hydrolysis of malononitrile with concentrated hydrochloric acid,2 by the hydration of carbon suboxide,3 and by the hydrolysis of cyanoacetic acid4 and its esters5 with potash. A method for the preparation of calcium malonate from chloroacetic acid and potassium cyanide is described by Fischer.6 Conrad7 liberated malonic acid from calcium malonate, so prepared, with oxalic acid. v. Miller,8 Grimaux and Tscherniak, and Bourgoin10 prepared malonic acid from chloroacetic acid and potassium cyanide, Petriev11 from... 

Self-Test 3.9A Describe the structure of the carbon suboxide molecule, C302, in terms of hybrid orbitals, bond angles, and tr- and -ir-bonds. The atoms lie in the order OCCCO. 

In carbon suboxide, for which the structure 6=C=C=C=o is most important, structures such as O—CsC—CsaO + contribute about... 

On thermolysis of bis(trimethylsilyl) malonate 337 at 160°C in the presence of P4O10 carbon suboxide 339 is formed in 54% yield, via 338 two equivalents of tri-mefhylsilanol 4 are also formed and react in situ with P4O10 to give polyphosphoric acid trimethylsilylester (PPSE) 195 [118] (Scheme 4.44). Pyrolysis of trimethylsilyl 2,2-dimefhylmalonate at 700°C gives dimethyl ketene and HMDSO 7 [118a]. 

Published sources do not mention any dangerous reactions with carbon suboxide, which is hardly ever used. 

The first synthesis of derivatives (77) of pentatetraene-carboxylic acid has been reported using a Wittig reaction of 1-H-allene-l,3-dicarboxylate monoester chlorides (76) in the presence of triethylamine.60 In one case an intermediate was obtained and was converted to (77) by further treatment with base. The reaction of carbon suboxide with phosphonium ylides has also... 

Malonyl dichloride has been prepared from malonic acid and thionyl chloride,4-9 and from carbon suboxide and anhydrous liquid hydrogen chloride.10 This procedure is based on that of Staudinger and Bereza 6 and of Backer and Homan.8... 

Reaction of urazoles 359 with carbon suboxide in dilute solutions (dioxane-MeCN 1 1, acetone, MeCN) provides 360, while in more concentrated solutions small yields (<25%) of 361 are also obtained (Scheme 54) <1995H(41)303>. 

Thiolactams 622 treated with carbon suboxide provide mesoionic compounds 623. Their 1,4-dipolar cycloaddition reaction with highly reactive PTAD gives compounds 624, formed by the cycloaddition followed by extrusion of COS, in quantitative yield (Scheme 100) <1995T6651, 1995H(41)1631>. 

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. 

This oxide (m.p. —111.3 and b.p. 7 °C), also known as carbon suboxide, C302, contains carbon in the formal oxidation state of +4/3. Because this is lower that its oxidation state in either CO or C02, the oxide is called carbon suboxide. The molecule is linear and has the structure... 

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. 

This interesting derivative of ketene is also obtained from benzilic acid by the old process of Staudinger the add is converted, by the action of phosphorus pentachloride, into diphenylchloracetyl chloride from which the two chlorine atoms are removed by means of zinc. (Formulate this equation.) What is carbon suboxide For information about the ketenes see H. Staudinger, Die Ketene, Stuttgart, 1912. 

---