Hymexazol是一种广泛用于农业的挥发性杀菌剂,导致其在大气中的丰富;因此,在评估其环境影响时,其大气命运和转换非常重要。在这里,我们报道了羟基自由基氧化hymexazol的理论动力学机制,以及通过在ROCBS-QB3//M06-2X上探索的势能面上使用基于Rice-Ramsperger-Kassel-Marcus的主方程动力学模型,以及其主要产物与O2然后与NO的后续反应。/aug-cc-pVTZ水平。预测的总速率常数ktotal(T,P)对于hymexazol和OH自由基之间的反应,与几乎无法获得的实验值显示出极好的一致性(例如,在T=300K和P=760Torr时,3.6×10-12vs(4.4±0.8)×10-12cm3/分子/s);因此,计算的动力学参数可以可靠地用于在大气甚至燃烧条件下的N-杂环相关应用的建模/模拟。模型显示3,4-二羟基-5-甲基-4,5-二氢-1,2-恶唑-5-基(IM2),3,5-二羟基-5-甲基-4,5-二氢-1,2-恶唑-4-基(IM3),和(3-羟基-1,2-恶唑-5-基)甲基(P8)是主要的主要中间体,形成(3,4-二羟基-5-甲基-4,5-二氢-1,2-恶唑-5-基)二氧化二烷基(IM4)的主要二级物种,(3,5-二羟基-5-甲基-4,5-二氢-1,2-恶唑-4-基)二氧杂烷基(IM7),和([(3-羟基-1,2-恶唑-5-基)甲基]二氧杂烷基(IM11),分别,通过与O2的反应。然后,主要的二级物种可以与NO反应形成主要的三级物种,即,(3,4-二羟基-5-甲基-4,5-二氢-1,2-恶唑-5-基)氧化烷基(P19),(3,5-二羟基-5-甲基-4,5-二氢-1,2-恶唑-4-基)氧化烷基(P21),和[(3-羟基-1,2-恶唑-5-基)甲基]氧化烷基(P23),分别,与NO2此外,hymexazol可能是对流层中的持久性有机污染物,因为其计算的半衰期τ1/2为13.7-68.1h,取决于海拔高度。
Hymexazol is a volatile fungicide widely used in agriculture, causing its abundance in the
atmosphere; thus, its atmospheric fate and conversion are of great importance when assessing its environmental impacts. Herein, we report a theoretical kinetic mechanism for the oxidation of hymexazol by OH radicals, as well as the subsequent reactions of its main products with O2 and then with NO by using the Rice-Ramsperger-Kassel-Marcus-based Master equation kinetic model on the potential energy surface explored at the ROCBS-QB3//M06-2X/aug-cc-pVTZ level. The predicted total rate constants ktotal(T, P) for the reaction between hymexazol and OH radicals show excellent agreement with scarcely available experimental values (e.g., 3.6 × 10-12 vs (4.4 ± 0.8) × 10-12 cm3/molecule/s at T = 300 K and P = 760 Torr); thus, the calculated kinetic parameters can be confidently used for modeling/simulation of N-heterocycle-related applications under atmospheric and even combustion conditions. The model shows that 3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl (IM2), 3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl (IM3), and (3-hydroxy-1,2-oxazol-5-yl)methyl (P8) are the main primary intermediates, which form the main secondary species of (3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl)dioxidanyl (IM4), (3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl)dioxidanyl (IM7), and ([(3-hydroxy-1,2-oxazol-5-yl)methyl]dioxidanyl (IM11), respectively, through the reactions with O2. The main secondary species then can react with NO to form the main tertiary species, namely, (3,4-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-5-yl)oxidanyl (P19), (3,5-dihydroxy-5-methyl-4,5-dihydro-1,2-oxazol-4-yl)oxidanyl (P21), and [(3-hydroxy-1,2-oxazol-5-yl)methyl]oxidanyl (P23), respectively, together with NO2. Besides, hymexazol could be a persistent organic pollutant in the troposphere due to its calculated half-life τ1/2 of 13.7-68.1 h, depending on the altitude.