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Theoretical investigation on the mechanisms and kinetics of OH-initiated photooxidation of dimethyl phthalate (DMP) in atmosphere

Han, Dandan, Li, Jing, Cao, Haijie, He, Maoxia, Hu, Jingtian, Yao, Side
Chemosphere 2014 v.95 pp. 50-57
chemical elements, dimethyl phthalate, equations, half life, hydroxyl radicals, hydroxylation, photooxidation, temperature
The atmospheric OH-initiated degradation mechanisms of dimethy phthalate (DMP) are analyzed at the MPWB1K/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) level of theory. The principal products detected experimentally are confirmed by this study while several major intermediates are reported for the first time. Additionally, the pathway scheme of hydroxylation reaction of DMP is proposed. The results about initial steps indicate that hydroxyl radical is most likely to be added to the ortho-carbon atom among additional reactions, while H atoms in methyl group are the most favorable to be abstracted by the OH radical. The rate constants of the elementary reactions over the temperature of 200–400K were deduced using RRKM theory. The overall rate constant of the title reaction is 1.18×10−12cm3molecule−1s−1 at 298K and 760Torr while H abstraction reactions predominate. According to the rate constants given at different temperatures, the Arrhenius equation is fitted. The atmospheric half life of DMP with respect to OH is estimated to be 6.8days.