Carbon dioxide dimerization

Bukowski R, Sadie] J, Jeziorski B, Jankowski P, Szalewicz K, Kucharski S A, Williams H L and Rice B M 1999 Intermolecular potential of carbon dioxide dimer from symmetry-adapted perturbation theory J. Chem. Phys. 110 3785... 

Several mechanisms for NCA polymerization have been proposed. NCAs may undergo nucleophilic attack at the amino acid carbonyl with loss of carbon dioxide to provide an amino acid derivative, which subsequently reacts with a second NCA to give dimer 1 and carbon dioxide. Dimer 1 then reacts with a third NCA and propagation continues until a high molecular weight polymer 2 is obtained.15-81 This mechanism is frequently referred to as normal NCA polymerization (Scheme 1). 

Muenter, J. S., An intermolecular potential function model applied to acetylene dimer, carbon dioxide dimer, and carbon dioxide acetylene, J. Chem. Phys. 94, 2781-2793 (1991). 

The existence of 1,2-dioxetandione (6) is still arguable. It was postulated as an intermediate in the chemiluminescent decomposition of oxalates with basic peroxide (Eq. 9), a reaction first discovered for oxalic chloride. Although its isolation was claimed in this reaction, no characteristic spectral data could be documented. The report that this carbon dioxide dimer was detected by mass spectrometry was shown to be erroneous. Consequently, this elusive species has so far defied synthesis and detection, and it seems urgent and timely to reinvestigate this challenging problem. 

At relatively low pressures below 10 GPa carbon dioxide remains purely molecular. Carbon-oxygen double bonds are highly stable and no transformation has been observed to 3000 K in phase I. On the other hand, there has been experimental evidence for which the direct elementary reaction of carbon and oxygen at about 2000 K and 9 GPa yields a nearly transparent ionic product of carbon dioxide dimer [75]. The fact that the ionic carbon dioxide dimer does not form directly from molecular carbon dioxide implies an existence of a large activation barrier for the dimerization pathway. However, once formed at high P and T, the dimer can be quenched to ambient temperature at high pressures. 

Treatment of oxalyl chloride with concentrated hydrogen peroxide under base catalysis in the presence of fluorescers leads to bright chemiluminescence.28 This rather unusual observation was also demonstrated for other oxalyl derivatives (9)29 and interpreted3 to involve 1,2-dioxetandione (3) as the intermediate [Eq. (7)]. Although isolation of the carbon dioxide dimer (3) was claimed,4 no characteristic spectral data could be observed.16 Furthermore, the claim30 of detecting... 

For the 1,2-dioxetanes the only characteristic band is the 0—0 deformation12,34 36,38 at 845-895 cm"1, but this band is weak and thus of limited value. Of great help is the characteristic carbonyl band at 1870 cm-1 for the a-peroxylactones.z It was not possible to observe an infrared spectrum of the carbon dioxide dimer 3.161... 

Although preliminary quantum-chemical calculations had predicted that the a-peroxylactones should be more stable than the simple 1,2-dioxetanes,32 the experimental data in Table III indicate the contrary.2,22 Moreover, thermokinetic calculations are in excellent accord with the experimental data.97b Thus, Richardson and co-workers97 predict activation energies of the order of 24-25 kcal for the 1,2-dioxetanes (1), 21-22 kcal for a-peroxylactones (2), and 17 kcal for the carbon dioxide dimer (3). 

By means of thermochemical calculations, O Neal and Richardson97 showed that sufficient energy is stored in the 1,2-dioxetanes (1), a-peroxylactones (2), and carbon dioxide dimer (3) to chemienergize carbonyl products in their electronically excited states. For 3 the available energy is only sufficient to produce triplet excited carbon dioxide. For the a-peroxylactones 2b, we concluded that the stored energy is sufficient only to energize singlet or triplet acetone, but not carbon diox-... 

Caprolactam Carboimidic difluoride Carbon dioxide dimer—water... 

Carbon disulfide—sulfiu dioxide complex Carbon monoselenide Carbon monosulfide Carbon monoxide Carbon monoxide dimer-water complex Carbon oxyselenide Carbon oxysulfide Carbon oxysulfide—carbon dioxide dimer complex Carbon oxysulfide—water complex... 

Scheme 27.2 Possible mechanism for HC03-H202-C02 chemiluminescence involving carbon dioxide dimer. DetaUs of the schematic principle are described in the text (Sagaya et al. 2009).

Brigot N, Odiot S, Wahnsley SH, Whitten JL (1977) The stmcture of the carbon dioxide dimer. Chem Phys Lett 49 157-159... 

Bukowski, R., Sadlej, J., Jeziorski, B., Jankowski, P., Szalewicz, K., Kucharski, S. A., Williams, H. L., Rice, B. M. (1999). Intermolecular potential of carbon dioxide dimer from symmetry-adapted perturbation theory. Journal of Chemical Physics, no, 3785-3803. 

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