Numerous processes in atmospheric and combustion chemistry produce the vinoxy radical (CHCHO). To understand the fate of this radical and to provide reliable energies needed for kinetic modeling of such processes, we have examined its reaction with O using highly reliable theoretical methods. Utilizing the focal point approach, the energetics of this reaction and subsequent reactions were obtained using coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)] extrapolated to the complete basis set limit. These extrapolated energies were appended with several corrections including a treatment of full triples and connected quadruple excitations, i.e., CCSDT(Q). In addition, this study models the initial vinoxy radical + O reaction for the first time with multireference methods. We predict a barrier for this reaction of approximately 0.4 kcal mol. This result agrees with experimental findings but is in disagreement with previous theoretical studies. The vinoxy radical + O reaction produces a 2-oxoethylperoxy radical which can undergo a number of unimolecular reactions. Abstraction of a β-hydrogen (a 1,4-hydrogen shift) and dissociation back to reactants are predicted to be competitive to each other due to their similar barriers of 21.2 and 22.3 kcal mol, respectively. The minimum-energy β-hydrogen abstraction pathway produces a hydroperoxy radical (QOOH) that eventually decomposes to formaldehyde, CO, and OH. Two other unimolecular reactions of the peroxy radical are α-hydrogen abstraction (38.7 kcal mol barrier) and HO elimination (43.5 kcal mol barrier). These pathways lead to glyoxal + OH and ketene + HO formation, respectively, but they are expected to be uncompetitive due to their high barriers.
Photobleaching of the halides of the triphenylmethane dyes crystal violet and malachite green in thin films of poly(methylmethacrylate) is described. The reaction proceeds via the triplet excited state of the dye which undergoes an intramolecular electron transfer reaction, forming the triarylmethyl and halogen free radicals. Quantum yields of triplet formation depend on the concentration of the dye which suggests that the intersystem crossing process involves more than one dye molecule. The rate of reaction depends on the rate at which radicals are formed which are free of the solvent cage and on the reactivity of the radicals.
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