Thermal Unimolecular Decomposition of Glyoxal

Article abstract of DOI:10.1021/j150650a033

The thermal unimolecular decomposition of glyoxal was investigated behind reflected shock waves in the temperature range 1100-1540 K, with argon as a diluent, by monitoring (CHO)2-absorption and CO-emission signals simultaneously.It was ascertained that glyoxal decomposed mainly via channel 1a, (CHO)2 -> 2CO + H2, and that the rate of channel 1b, (CHO)2 -> CH2O + CO, was relatively low under the present conditions.The reaction took place in the falloff region when total density was changed from 2.8 X 1E-6 to 3.5 X 1E-5 mol cm^-3.From the theory of unimolecular reaction, the rate constants for the main channel were determined as k_infinite = 1E14.03 exp(-55.1 kcal mol^-1/RT)s^-1 in the high-pressure limit and k₀/ = 1E16.41 exp(-38.4 kcal mol^-1/RT) cm³ mol^-1 s^-1 in the low-pressure limit, respectively.The values of k_infinite were well connected with the previous data obtained at lower temperatures by using a static method.The fact that channel 1a is more dominant than channel 1b is consistent with ab initio calculations by Osamura et al.