Chow Ronald, Mok Daniel K W
Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong.
Phys Chem Chem Phys. 2020 Jul 7;22(25):14130-14141. doi: 10.1039/d0cp00961j. Epub 2020 Jun 16.
The reaction of hydroxymethyl hydroperoxide (HMHP, HOCHOOH) with the simplest Criegee intermediate, CHOO, has been examined using quantum chemical methods with transition state theory. Geometry optimization and IRC calculations were performed using the M06-2X, MN15-L, and B2PLYP-D3 functionals in conjunction with the aug-cc-pVTZ basis set. Single point energy calculations using QCISD(T) and BD(T) with the same basis set have been performed to determine the energy of reactants, reactive complexes, transition states, and products. Rate coefficients have been obtained using variational transition state theory. The addition of CHOO on the three different oxygen atoms in HMHP has been considered and the ether oxide forming channel, CHOO + HOCHOOH → HOCHO(O)CHOOH (channel 2), is the most favorable. The best computed standard enthalpy of reaction (ΔH) and zero-point corrected barrier height are -20.02 and -6.33 kcal mol, respectively. The reaction barrier is negative and our results suggest that both the inner and outer transition states contribute to the corresponding overall reactive flux in the tropospheric temperature range (220 K to 320 K). A two-transition state model has been used to obtain reliable rate coefficients at the high-pressure limit. The pressure-dependent rate coefficient calculations using the SS-QRRK theory have shown that this channel is pressure-dependent. Moreover, our investigation has shown that the ether oxide formed may rapidly react with SO at 298 K to form SO, which can, in turn, react with water to form atmospheric HSO. A similar calculation has been conducted for the reaction of HMHP with OH, suggesting that the titled reaction may be a significant sink of HMHP. Therefore, the reaction between CHOO and HOCHOOH could be an indirect source for generating atmospheric HSO, which is crucial to the formation of clouds, and it might relieve global warming.
采用量子化学方法结合过渡态理论研究了羟甲基过氧化氢（HMHP，HOCHOOH）与最简单的克里奇中间体CHOO的反应。使用M06 - 2X、MN15 - L和B2PLYP - D3泛函结合aug - cc - pVTZ基组进行几何优化和内禀反应坐标（IRC）计算。使用相同基组的QCISD(T)和BD(T)进行单点能量计算，以确定反应物、反应复合物、过渡态和产物的能量。采用变分过渡态理论获得速率系数。考虑了CHOO在HMHP中三个不同氧原子上的加成，形成环氧醚的通道CHOO + HOCHOOH → HOCHO(O)CHOOH（通道2）是最有利的。计算得到的最佳反应标准焓（ΔH）和零点校正势垒高度分别为 - 20.02和 - 6.33 kcal/mol。反应势垒为负，我们的结果表明，在对流层温度范围（220 K至320 K）内，内过渡态和外过渡态都对相应的总反应通量有贡献。采用双过渡态模型在高压极限下获得可靠的速率系数。使用稳态 - 准正则变分过渡态理论（SS - QRRK理论）进行的压力依赖速率系数计算表明，该通道与压力有关。此外，我们的研究表明，在298 K时，形成的环氧醚可能会与SO迅速反应形成SO，进而与水反应形成大气中的HSO。对HMHP与OH的反应进行了类似计算，表明该反应可能是HMHP的一个重要消耗途径。因此，CHOO与HOCHOOH之间的反应可能是大气中HSO生成的间接来源，这对云的形成至关重要，并且可能缓解全球变暖。
