Bhattacharjee Debajyoti, Mishra Bhupesh Kumar, Deka Ramesh Chandra
Department of Chemical Sciences, Tezpur University, Tezpur, Napaam, Assam, 784028, India.
J Mol Model. 2015 Apr;21(4):69. doi: 10.1007/s00894-015-2629-x. Epub 2015 Mar 7.
In the present work, theoretical study on the mechanism and kinetics of the gas-phase reactions of CF3CF2CH2OCH3 (HFE-365mcf3) with the OH radicals have been performed using meta-hybrid modern density functional M06-2X in conjunction with 6-31+G(d,p) basis set. Reaction profiles for OH-initiated hydrogen abstraction are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels. Our calculations reveal that hydrogen abstraction from the -CH2 group is thermodynamically more facile than that from the -CH3 group. This is further ascertained by the calculated C-H bond dissociation energy of CF3CF2CH2OCH3 molecule. The rate constants of the titled reactions are computed over the temperature range of 250-450 K. The calculated rate constant value at 298 K is found to be in reasonable agreement with the experimental results. The atmospheric life time of HFE-365mcf3 is estimated to be 42 days. The atmospheric fate of the alkoxy radicals, CF3CF2CH(O(•))OCH3 and CF3CF2CH2OCH2O(•) 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 the dominant atmospheric sink for the decomposition of CF3CF2CH(O(•))OCH3 radical in the atmosphere.
在本工作中，使用meta-杂化现代密度泛函M06-2X并结合6-31+G(d,p)基组，对CF3CF2CH2OCH3（HFE-365mcf3）与OH自由基的气相反应机理和动力学进行了理论研究。对OH引发的氢提取反应剖面进行了建模，包括在入口和出口通道形成预反应和后反应复合物。我们的计算表明，从-CH2基团提取氢在热力学上比从-CH3基团提取更易进行。这通过计算CF3CF2CH2OCH3分子的C-H键解离能得到了进一步证实。计算了标题反应在250 - 450 K温度范围内的速率常数。发现在298 K时计算得到的速率常数与实验结果合理吻合。估计HFE-365mcf3的大气寿命为42天。还首次使用相同的理论水平研究了烷氧基自由基CF3CF2CH(O(•))OCH3和CF3CF2CH2OCH2O(•)的大气归宿。在三个可能的分解通道中，我们的结果明确指出，与O2反应是大气中CF3CF2CH(O(•))OCH3自由基分解的主要大气汇。
