Aroeira Gustavo J R, Abbott Adam S, Elliott Sarah N, Turney Justin M, Schaefer Henry F
Center for Computational Quantum Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, USA.
Phys Chem Chem Phys. 2019 Aug 28;21(32):17760-17771. doi: 10.1039/c9cp03480c. Epub 2019 Aug 1.
Bimolecular reactions involving stabilized Criegee intermediates (SCI) have been the target of many studies due to the role these molecules play in atmospheric chemistry. Recently, kinetic rates for the addition reaction of the simplest SCI (formaldehyde oxide) and its methylated analogue (acetone oxide) with methanol were reported both experimentally and theoretically. We re-examine the energy profile of these reactions by employing rigorous ab initio methods. Optimized CCSD(T)/ANO1 geometries are reported for the stationary points along the reaction path. Energies are obtained at the CCSD(T)/CBS level of theory. Contributions of full triple and quadruple excitations are computed to assess the convergence of this method. Rate constants are obtained using conventional canonical transition state theory under the rigid rotor harmonic oscillator approximation and with the inclusion of a one-dimensional hindered rotor treatment. These corrections for internal rotations have a significant impact on computed kinetic rate constants. With this approach, we compute rate constants for the addition of methanol to formaldehyde oxide (HCOO) and acetone oxide [(CH)COO] at 298.15 K as (1.2 ± 0.8) × 10 and (2.8 ± 1.3) × 10 cm s, respectively. Additionally, we investigate the temperature dependence of the rate constant, concluding that the transition state barrier height and tunneling contributions shape the qualitative behaviour of these reactions.
由于稳定的克里吉中间体（SCI）在大气化学中所起的作用，涉及这些分子的双分子反应一直是许多研究的目标。最近，报道了最简单的SCI（氧化甲醛）及其甲基化类似物（氧化丙酮）与甲醇加成反应的动力学速率，包括实验和理论方面的报道。我们采用严格的从头算方法重新审视这些反应的能量分布。报告了沿反应路径各驻点的优化CCSD(T)/ANO1几何结构。能量是在CCSD(T)/CBS理论水平上获得的。计算了全三重和四重激发的贡献，以评估该方法的收敛性。速率常数是在刚性转子谐波振荡器近似下，采用传统的正则过渡态理论，并包括一维受阻转子处理来获得的。这些内部旋转校正对计算得到的动力学速率常数有显著影响。通过这种方法，我们计算了在298.15 K时甲醇与氧化甲醛（HCOO）和氧化丙酮[(CH)COO]加成反应的速率常数，分别为(1.2 ± 0.8) × 10和(2.8 ± 1.3) × 10 cm s。此外，我们研究了速率常数的温度依赖性，得出结论：过渡态势垒高度和隧穿贡献决定了这些反应的定性行为。
