Li Ming-Yi, Bai Feng-Yang, Pan Xiu-Mei
Institute of Functional Material Chemistry, National & Local United Engineering Lab for Power Battery, Faculty of Chemistry, Northeast Normal University, 130024, Changchun, People's Republic of China.
Institute of Catalysis for Energy and Environment, College of Chemistry and Chemical Engineering, Shenyang Normal University, Shenyang, 110034, People's Republic of China.
J Mol Graph Model. 2019 Dec;93:107453. doi: 10.1016/j.jmgm.2019.107453. Epub 2019 Sep 21.
The nocturnal reactions of CHCHOCHCH, CHFCFOCHCF and CFCHOCH initiated by NO radicals are important sources of alkyl radicals and nitric acids. In this paper, the thermodynamics and kinetics of CHCHOCHCH, CHFCFOCHCF and CFCHOCH induced by NO radical in gas phase are studied in detail by BHandHLYP method combined with 6-311G(d,p) basis set, and the single point correction is calculated by relatively accurate CCSD(T) method. In the temperature range of 200-400 K, the rate constants of title reactions are fitted to the three-parameter Arrhenius formula: k = 1.13 × 10Texp(1675.99/T) k = 2.23 × 10Texp(-4476.24/T) k = 5.63 × 10Texp(-9344.12/T) All the rate constants calculated by the canonical variational transition state theory and the small curvature tunneling are basically consistent with the limited experimental data. By comparing the reaction rate constants of ethyl ether and its isomer methyl propyl ether with NO radical at 293 ± 2 K, the higher the symmetry is, the faster the reaction rate of ether is. Thermodynamic calculations and kinetic data of the title reactions indicate that the H-abstraction reactions at the -OCH- sites are the main reaction pathways. The thermodynamic and kinetic data of the reaction CHCHOCHCH, CHFCFOCHCF with NO radical, showing that the reaction activity could be reduced due to the addition of fluorine atoms, which is further verified by the enthalpies, Gibbs free energies of the title reactions and C-H bond dissociation energies of the CHCHOCHCH, CHFCFOCHCF and CFCHOCH molecules. The reaction thermodynamics and kinetics are determined, and the formation mechanisms of the products are proposed, which are crucial to determine the influence of CHCHOCHCH, CHFCFOCHCF and CFCHOCH on air quality, as well as its atmospheric lifetime and durability. The atmospheric lifetimes of CHCHOCHCH, CHFCFOCHCF and CFCHOCH are evaluated in the NO-concentration range of 5 × 10-2 × 10 molecule cm to fully consider the effects of different regions on their nocturnal migration. The radiation efficiency and global warming potentials (GWPs) have been reported. The products of title reaction CHCHOCHCH, CFCHOCFCHF and CFCHOCH are further oxidized into organic nitrates in the presence of O and NO. Organic nitrites can be isomerized into organic nitrates or degraded to form CHC(O•)HOCHCH, CFC(O•)HOCFCHF and CHC(O•)HOCF alkoxy radicals and NO. This work provides deep insight into the night migration and transformation mechanism of the three ethers.
由NO自由基引发的CHCHOCHCH、CHFCFOCHCF和CFCHOCH的夜间反应是烷基自由基和硝酸的重要来源。本文采用BHandHLYP方法结合6-311G(d,p)基组，详细研究了气相中NO自由基诱导CHCHOCHCH、CHFCFOCHCF和CFCHOCH的热力学和动力学，并通过相对精确的CCSD(T)方法进行单点校正。在200-400 K温度范围内，将标题反应的速率常数拟合为三参数Arrhenius公式：k = 1.13×10Texp(1675.99/T) k = 2.23×10Texp(-4476.24/T) k = 5.63×10Texp(-9344.12/T) 采用正则变分过渡态理论和小曲率隧道效应计算得到的所有速率常数与有限的实验数据基本一致。通过比较293±2 K下乙醚及其异构体甲基丙基醚与NO自由基的反应速率常数，发现醚的对称性越高，反应速率越快。标题反应的热力学计算和动力学数据表明，-OCH-位点的H抽取反应是主要反应途径。CHCHOCHCH、CHFCFOCHCF与NO自由基反应的热力学和动力学数据表明，氟原子的加入会降低反应活性，这通过标题反应的焓、吉布斯自由能以及CHCHOCHCH、CHFCFOCHCF和CFCHOCH分子的C-H键解离能得到进一步验证。确定了反应热力学和动力学，提出了产物的形成机制，这对于确定CHCHOCHCH、CHFCFOCHCF和CFCHOCH对空气质量的影响及其大气寿命和持久性至关重要。在5×10-2×10分子/cm的NO浓度范围内评估了CHCHOCHCH、CHFCFOCHCF和CFCHOCH的大气寿命，以充分考虑不同区域对其夜间迁移的影响。报道了辐射效率和全球变暖潜能值（GWPs）。标题反应CHCHOCHCH、CFCHOCFCHF和CFCHOCH的产物在O和NO存在下进一步氧化为有机硝酸盐。有机亚硝酸盐可异构化为有机硝酸盐或降解形成CHC(O•)HOCHCH、CFC(O•)HOCFCHF和CHC(O•)HOCF烷氧基自由基和NO。这项工作为三种醚的夜间迁移和转化机制提供了深入的见解。
