科研之友
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摘要
The reaction mechanisms for ozonolysis of ethyl vinyl ether (EVE) and propyl vinyl ether (PVE) have been investigated using the density functional theory (DFT) and ab initio method. Cycloaddition reactions of O-3 to EVE and PVE are highly exothermic by 52.91 and 53.17 kcal/mol, respectively. Major products (formaldehyde, ethyl formate, and propyl formate) resulting from the both reactions are identified by comparing them with the experimental results. Further reactions of the most energy-rich Criegee intermediates (C2H5OCHOO and C3H7OCHOO) have been proposed in the presence of NO and H2O in which the main products are ethyl formate and propyl formate. The Multichannel Rice-Ramsperger-Kassel-Marcus (RRKM) approach is employed to calculate the total and individual rate constants for major product channels over a wide range of temperatures and different pressures. In the temperature range of 200-2500 K, the main path is the production of ethyl formate with k (EVE+O3) = 4.67 x 10(-12) exp(-3029/T), for the EVE with O-3 reaction and k (PVE+O3) = 3.58 x 10(-12) exp(-2858/T) for the PVE with O-3 reaction. At 298 K and 760 torr, the rate constants calculated are 1.80 x 10(-16) and 2.45 x 10(-16) cm(3) molecule(-1) s(-1) for ozonolysis of EVE and PVE, which are consistent with the experimental results. The total rate constants show positive temperature dependence over the temperature range of 200-2000 K but pressure independence in the range of 0.01-10000 Torr. Estimation of branching ratios of several products is also performed. The influence of carbon chain length on reactivity toward ozone is examined.
- 出版日期2012-4
- 单位山东大学
