Department of Chemical Sciences, Tezpur University, Tezpur, Assam 784028, India.
Department of Chemistry, North-Eastern Hill University, Shillong 793022, India.
J Mol Graph Model. 2014 May;50:90-9. doi: 10.1016/j.jmgm.2014.03.009. Epub 2014 Apr 5.
Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF3CH2OCH3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction from the CH2 group is thermodynamically and kinetically more facile than that from the CH3 group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF3CH2OCH3 and radicals (CF3CHOCH3 and CF3CH2OCH2) are also reported for the first time. The calculated bond dissociation energies for the CH bonds are in good agreement with experimental results. At 298K, the calculated total rate coefficient for CF3CH2OCH3+OH reactions is found to be in good agreement with the experimental results. The atmospheric fate of the alkoxy radicals, CF3CH(O)OCH3 and CF3CH2OCH2O are also investigated for the first time using the same level of theory. Out of three plausible decomposition channels, our results clearly point out that reaction with O2 is not the dominant path leading to the formation of CF3C(O)OCH3 for the decomposition of CF3CH(O)OCH3 radical in the atmosphere. This is in accord with the recent report of Osterstrom et al. [CPL 524 (2012) 32] but found to be in contradiction with experimental finding of Oyaro et al. [JPCA 109 (2005) 337].
已使用从头算和 DFT 方法对 CF3CH2OCH3（HFE-263fb2）与 OH 自由基在气相中的反应的机理、动力学和热化学进行了详细的理论研究。反应途径包括在入口和出口通道中分别形成预反应和后反应络合物。我们的计算表明，CH2 基团上的氢提取在热力学和动力学上比 CH3 基团上的氢提取更容易。使用基团平衡等电子反应，首次报道了 CF3CH2OCH3 和自由基（CF3CHOCH3 和 CF3CH2OCH2）的标准生成焓。计算的 CH 键键离解能与实验结果吻合良好。在 298K 下，计算得到的 CF3CH2OCH3+OH 反应的总速率常数与实验结果吻合良好。首次使用相同的理论水平研究了烷氧基自由基 CF3CH(O)OCH3 和 CF3CH2OCH2O 的大气命运。在三个可能的分解通道中，我们的结果清楚地指出，对于 CF3CH(O)OCH3 自由基在大气中的分解，与 O2 的反应不是导致 CF3C(O)OCH3 形成的主要途径。这与 Osterstrom 等人的最新报告[CPL 524（2012）32]一致，但与 Oyaro 等人的实验结果[JPCA 109（2005）337]相矛盾。
