Chow Ronald, Mok Daniel K W, Lee Edmond P F, Dyke John M
Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong.
School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
Phys Chem Chem Phys. 2021 Mar 18;23(10):6309-6315. doi: 10.1039/d0cp00222d.
The reaction, BrO + HO2 → HOBr + O2, is exothermic and can produce O2 in both its ground state (X[combining tilde]3∑g-) and its first excited state (ã1Δg). As a result, this reaction can proceed on both a singlet and a triplet potential energy surface. Recently, Tsona, Tang and Du published a paper entitled "Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products (Phys. Chem. Chem. Phys. 2019, 21, 20296-203072). The results of this work showed significant differences from those published earlier on this reaction by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569). Further calculations performed in this present work, combined with higher level calculations published by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569), demonstrate that the work of Tsona et al. is flawed because the integration grid size used in their lowest singlet and triplet calculations is too small, and a closed-shell wavefunction, rather than an open-shell wavefunction, has been used for the singlet surface. The major conclusion in the work of Tsona et al. that the lowest singlet and triplet channels are barrierless is shown to be incorrect. Also, the computed rate coefficients of Tsona et al. showed a positive temperature dependence, which is inconsistent with the experimentally observed negative temperature dependence, whereas the singlet rate coefficients computed by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569) showed a negative temperature dependence consistent with experiment.
反应BrO + HO₂ → HOBr + O₂是放热反应，并且能够产生基态（X[合并波浪号]³∑g⁻）和第一激发态（ã¹Δg）的O₂。因此，该反应可以在单重态和三重态势能面上进行。最近，特索纳、唐和杜发表了一篇题为《水对BrO + HO₂气相反应的影响：机理、动力学和产物》（《物理化学化学物理》，2019年，21卷，20296 - 203072页）的论文。这项工作的结果与乔等人（《物理化学化学物理》，2016年，18卷，30554 - 30569页）早期发表的关于该反应的结果存在显著差异。本工作中进行的进一步计算，结合乔等人（《物理化学化学物理》，2016年，18卷，30554 - 30569页）发表的更高水平的计算，表明特索纳等人的工作存在缺陷，因为他们在最低单重态和三重态计算中使用的积分网格尺寸太小，并且在单重态势面上使用的是闭壳层波函数，而不是开壳层波函数。特索纳等人工作中的主要结论，即最低单重态和三重态通道无势垒，被证明是不正确的。此外，特索纳等人计算的速率系数表现出正的温度依赖性，这与实验观察到的负温度依赖性不一致，而乔等人（《物理化学化学物理》，2016年，18卷，30554 - 30569页）计算的单重态速率系数表现出与实验一致的负温度依赖性。
