A gas-phase mechanistic investigation of the unimolecular, water/ammonia-assisted decomposition reactions of the α-hydroxy hydroperoxides (HPs) and hydroperoxide arylamines (a-HPs) produced during the styrene ozonolysis has been carried out theoretically in the present article. The instrumental role of stereochemistry in controlling the outcome of individual reactions has been discussed. Thermodynamic parameters (ΔG_298K, ΔH_298K, ΔE_0K) associated with individual reactions have also been computed. The rate constants estimated for individual reactions using conventional transition state theory (TST) combined with statistical mechanics provide a comprehensive understanding of the reaction mechanism and also elucidate the atmospheric fate of Criegee intermediates. Considering the feasibility of reactions from thermodynamic and kinetic points of view, while aldehyde (PhCHO) formation pathway originating from bimolecular decomposition of HP is found to be kinetically favored, benzoic acid formation pathway remains favored thermodynamically. A similar consideration for the bimolecular reactions of a-HP reveals the phenylmethanimine formation pathway to be kinetically favored, while the benzamide formation pathway is favored thermodynamically. Our findings appear to be in excellent agreement with the experimental observations.

中文翻译：

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在H ₂ O和NH ₃存在下苯乙烯臭氧分解过程中形成的中间体中间体的大气命运：立体化学的关键作用

从理论上讲，已经对苯乙烯臭氧分解过程中产生的α-羟基氢过氧化物（HPs）和氢过氧化物芳基胺（a-HPs）的单分子水/氨辅助分解反应进行了气相机理研究。已经讨论了立体化学在控制单个反应结果中的工具作用。热力学参数（ΔG _298K，ΔH _298K，ΔE _0K与个别反应相关的）也已计算出来。使用常规的过渡态理论（TST）结合统计力学为单个反应估算的速率常数提供了对反应机理的全面理解，还阐明了Criegee中间体的大气命运。从热力学和动力学的观点考虑反应的可行性，虽然发现从HP的双分子分解开始的醛（PhCHO）形成途径在动力学上是有利的，但是苯甲酸的形成途径在热力学上仍然是有利的。对a-HP的双分子反应的类似考虑表明，动力学上有利于苯甲胺的形成途径，而热力学上有利于苯甲酰胺的形成途径。