Carbon suboxide polymerization

Carbon suboxide, C3O2, 0=C=C=C=0 , also called l,2-propadiene-l,3-dione, is an evil-smelling unstable gas, bp +6.8 °C, which is obtained by the dehydration of malonic acid with P4O10 in vacuum at 140-150 °C (equation 6). Carbon suboxide polymerizes readily at room temperature to a yellow solid, and above 100 °C to a ruby-red water-soluble solid. Photolysis of C3O2 gives C2O ( C=C=0 ) as a reactive intermediate, which reacts with alkenes by carbon atom insertion (equation 7). 

Carbon suboxide polymerizes readily at temperatures above —78°C. An e.d. study indicates a linear molecule with C-C, 1-28 A, and C-0, 1-16 but the possibility of small deviations from linearity could not be excluded. 

Carbon suboxide, polymerization of, 131 Catalytic activity of, polymeric metal phthalocyanines, 159 o-Carboxybenzaldehyde, polymers with ferrocene, 128,129 4-Carboxy-1,6-heptadiene, polymers of, 79 Chelate polymers, 173,327 Chlorendic acid,... 

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. 

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. 

As expected, the reaction of C3O2 with water produces malonic acid. Carbon suboxide bums readily, and although it is stable at -78 °C, it polymerizes at 25 °C. 

Carbon suboxide (C302),50 an evil-smelling gas, is formed by dehydrating mal-onic acid with P2Os in vacuum at 140 to 150°C, or better, by thermolysis of diacetyltar-taric anhydride. The molecule is linear and can be represented by the structural formula 0=C=C=C=0. It is stable at -78°C, but at 25°C it polymerizes, forming yellow to violet products. Photolysis of Q02 gives QO, which will react with olefins ... 

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]. 

Carbon suboxide, 0 OC=C=0, an unusually reactive bisketene, functions as an efficient double electrophile, in the synthesis of heterocyclic compounds (1). One would expect that the molecule, having four cumulative ir bonds, should be of considerable interest in the field of polymer chemistry and should have been investigated vigorously. On the contrary, not only has the structure of its polymer not been unequivocally established, but also the physical properties of the polymer and the kinetics and mechanism of the polymerization process have not been studied to any significant extent, even though its polymerization product... 

Polymerization of carbon suboxide in heterogeneous systems, i.e. polymer precipitating from the reaction solution, by various initiators was examined qualitatively by Hegar (9). It was found that the best catalysts in cyclohexane solution (at 0°C., then room temperature) were triethylamine and pyridine. Boron trifluoride was somewhat less effective, while sulfuric acid was inefficient and slow. With aluminum chloride the catalyst particles were rapidly coated with polymer, and no significant amount of polymer could be obtained. 

Solution Polymerization. Dimethyl formamide, DMF, is a good solvent for poly(carbon suboxide) with DP lower than six and hence can serve as an effective medium for the kinetic studies of solution polymerization. The use of a polymer solvent such as... 

This is the same rate law obtained by Smith (6) and Blake (7) for the gas phase polymerization. This supports the conclusion that the paramagnetism is a property of the carbon suboxide polymer in the solid state and is not due to formation of a side product. It was further confirmed by parallel measurements of the ESR signal intensity and optical absorbances of the polymer at 370 nm and 4.6 ym at various spin concentrations. The spin density was related linearly to the optical densities. The possibility that the paramagnetism is due to a buried radical intermediate is precluded by evidence that propagation does not involve a radical intermediate (vide infra). 

Retardation and Inhibition. In order to obtain additional information on the polymerization process, various potential inhibitors or retarding agents were added to carbon suboxide, and the rate of polymer deposition from the gas phase was quantitatively studied at 100°C. To the monomer at a pressure of 330 mm Hg was added either an equimolar quantity of inhibitor based on pressure measurements, or room temperature vapor pressure of additive if less than 330 mm Hg. The additives used were oxygen, nitric oxide, 3-methyl-1-butene, 1,3-butadiene, acetone and acetaldehyde. Polymerization rates were followed by ESR measurements. 

Carbon suboxide s susceptibility to radical polymerization was also examined by an attempted copolymerization of equimolar quantities of carbon suboxide and styrene initiated by azobisisobutyronitrile at 60°C in toluene solution. The infrared spectrum of the polymeric product was identical with that of a styrene homopolymer control, and no carbonyl absorption was detected. 

On the basis of these observations it is concluded that the polymerization does not involve a propagating reactive radical species. It is unlikely that carbon suboxide monomer would be attacked by the paramagnetic polymer species since C3O2 is inert to radicals as reactive as the styryl radical while the paramagnetic polymer is not reactive enough to attack the nitrone spin trap. 

Significant retardation was observed with the alkene additives and particularly with acetone or acetaldehyde. It has been experimentally observed that carbon suboxide prepared by the pyrolysis of diacetyltartaric anhydride is more stable toward polymerization than that prepared by the dehydration of malonic acid. We have observed infrared impurity bands at 3.65, 5.75,... 

Solution Polymerization (21). Solution polymerization of carbon suboxide in DMF was followed by monitoring the absorbance of the system at 420, 500 and 600 nm. At all three wavelengths a plot of the square root of the absorbance against time was linear indicating a reaction order of 1/2 with respect to polymer (Figure 2). The reaction order with respect to monomer... 

In the polymerization of carbon suboxide, the monomer molecules are incorporated into the polymer ladder as a part of a six-membered ring (Figure 1-b). Here both the electrophilic and the nucleophilic sites of the carbon suboxide molecule must participate in the reaction. In the initiation step, the first monomer is also required to assume a bent geometry, since two linear molecules colliding to form a six-membered ring is very unlikely due to the unfavorable spatial orientation. 

Mechanism of Polymerization. A mechanism for polymerization of carbon suboxide was suggested by Ziegler (8) involving initiation by water or acetic acid, with the formation of an... 

It was suggested by Ulrich (39) that the polymer could arise from an initial noncatalyzed formation of a dimer which would further react with carbon suboxide to give polymer. A conjugated carbon backbone may be formed by [4 + 2] cycloaddition of a growing polymeric a-acylketene with monomer. 

It is clear that further work will be required to elucidate the details of the mechanistic pathway for the polymerization of carbon suboxide. Both the mechanism proposed by Ulrich (39) and the above zwitterionic mechanism lead to a functionality of two ketenyl groups per molecule. 

Miscellaneous Routes. Polyamides have been prepared by other reactions, including addition of amines to activated double bonds, polymerization of isocyanates, reaction of formaldehyde with dinitriles, reaction of dicarboxylic acids with dllsocyanates, reaction of carbon suboxide with diamines, and reaction of diazlactones with diamines. These reactions are reviewed in Reference 4. 

Carbon suboxide is a gas, which possesses a pungent odor and can be condensed to a liquid which boils at —7°. It polymerizes on standing to a dark red amorphous substance. It is converted rapidly by water into malonic acid. 

It is a gas that liquefies at —56°. It bears the same relation to acetic acid that carbon suboxide does to malonic acid it adds water directly and is thereby converted into acetic acid. The double bond which it contains is a very active one. Ketene polymerizes readily and adds directly to a number of elements and compounds. It unites with alcohol and forms ethyl acetate, and with ammonia to form acetamide. 

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... 

---