Improved computational modeling of the kinetics of the acetylperoxy + HO 2 reaction
Improved computational modeling of the kinetics of the acetylperoxy + HO 2 reaction
复制标题
改进的乙酰过氧 HO 2 反应动力学计算模型
DOI：
10.1039/d2fd00030j
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发表时间：
2022
影响因子：
3.4
通讯作者：
Claypool, Duncan J.
中科院分区：
文献类型：
--
作者：
Kuwata, Keith T.;DeVault, Marla P.;Claypool, Duncan J.
乙酰过氧+ HO2反应对对流层有多重影响，三重态途径导致过氧+ O2（反应（1a））与单线态途径导致乙酸+ O3（反应（1b））和乙酰过氧+ OH + O2（反应（1c））竞争。最近的一项实验研究报道了这三种途径（α1a， α1b和α1c）在229 K到294 K之间的分支分数。我们利用量子化学和Rice-Ramsperger-Kassel-Marcus /master equation （RRKM/ME）模拟构建了预测α1a、α1b和α1c的理论模型。我们的主要量子化学方法是Weizmann-1 Brueckner double （W1BD）理论；我们结合W1BD和运动方程自旋-翻转耦合簇（SF）理论来研究开壳单重态结构。采用RRKM/ME模拟，包括乙酰过氧- ho2预反应配合物的所有构象，得到了298 K的三态速率常数，k1a = 5.11 × 10−12 cm3 / s /分子，α1a值与实验结果非常吻合。将所有单线态结构的能量增加0.9 kcal mol−1，得到的单线态速率常数为k1b+1c = 1.20 × 10−11 cm3 / s，与实验结果吻合较好。然而，我们预测的α1b和α1c随温度的变化并不像实际测量的那么大，这可能是由于SF理论在处理控制醋酸+ O3形成与乙酰氧基+ OH + O2形成的过渡结构方面的不足。
The acetylperoxy + HO2 reaction has multiple impacts on the troposphere, with a triplet pathway leading to peracetic acid + O2 (reaction (1a)) competing with singlet pathways leading to acetic acid + O3 (reaction (1b)) and acetoxy + OH + O2 (reaction (1c)). A recent experimental study has reported branching fractions for these three pathways (α1a, α1b, and α1c) from 229 K to 294 K. We constructed a theoretical model for predicting α1a, α1b, and α1c using quantum chemical and Rice–Ramsperger–Kassel–Marcus/master equation (RRKM/ME) simulations. Our main quantum chemical method was Weizmann-1 Brueckner Doubles (W1BD) theory; we combined W1BD and equation-of-motion spin-flip coupled cluster (SF) theory to treat open-shell singlet structures. Using RRKM/ME simulations that included all conformers of acetylperoxy–HO2 pre-reactive complexes led to a 298 K triplet rate constant, k1a = 5.11 × 10−12 cm3 per molecule per s, and values of α1a in excellent agreement with experiment. Increasing the energies of all singlet structures by 0.9 kcal mol−1 led to a combined singlet rate constant, k1b+1c = 1.20 × 10−11 cm3 per molecule per s, in good agreement with experiment. However, our predicted variations in α1b and α1c with temperature are not nearly as large as those measured, perhaps due to the inadequacy of SF theory in treating the transition structures controlling acetic acid + O3 formation vs. acetoxy + OH + O2 formation.