Reactions of (CO2)2+ and (CO)2+ association ions

The reactons of (CO₂)₂⁺ and (CO)₂⁺ with various additives have been investigated using the NBS high-pressure photoionization mass spectrometer at total pressures of 0.4–1.0 torr of either CO₂ or CO. The additives include CH₄, CD₄, C₂H₂, O₂, H₂O, ^15,14N₂O, and CO in both CO₂ and ¹³CO₂. Second- and third-order rate coefficients based on an ambipolar diffusion model are reported for 25 separate reaction pairs at 295°K, as well as sequential cationic reaction mechanisms. An approximate value of 225 ± 3 kcal/mol (941 ± 13 kJ/mol) was derived for ΔH_f (CO)₂⁺ based on the kinetics observed in various CO-additive mixtures. Some projections regarding the utility of the data under other conditions are also included.