Watching a hydroperoxyalkyl radical (•QOOH) dissociate
Watching a hydroperoxyalkyl radical (•QOOH) dissociate
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DOI：
10.1126/science.abj0412
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发表时间：
2021-08-06
期刊：
影响因子：
56.9
通讯作者：
Lester, Marsha, I
中科院分区：
文献类型：
--
作者：
Hansen, Anne S.;Bhagde, Trisha;Lester, Marsha, I
通过其红外指纹和能量依赖性单分子衰变成羟基自由基和环醚产物，直接观察到在挥发性有机化合物的氧化过程中瞬时形成的原型氢过氧烷基自由基（中心点QOOH）中间体。发现在较宽的能量范围内对中心点 QOOH 单分子解离速率的直接时域测量与使用过渡态势垒区的最先进的电子结构表征进行的理论预测一致。单分子衰变通过大量的重原子隧道增强，涉及沿反应路径的 O-O 伸长和 C-C-O 角收缩。主方程建模对中心点 QOOH 中间体的压力依赖性热单分子解离速率进行了完全先验的预测（再次通过重原子隧道效应增加），这是大气和燃烧化学的全局模型所必需的。
A prototypical hydroperoxyalkyl radical (center dot QOOH) intermediate, transiently formed in the oxidation of volatile organic compounds, was directly observed through its infrared fingerprint and energy-dependent unimolecular decay to hydroxyl radical and cyclic ether products. Direct time-domain measurements of center dot QOOH unimolecular dissociation rates over a wide range of energies were found to be in accord with those predicted theoretically using state- of-the-art electronic structure characterizations of the transition state barrier region. Unimolecular decay was enhanced by substantial heavy-atom tunneling involving O-O elongation and C-C-O angle contraction along the reaction pathway. Master equation modeling yielded a fully a priori prediction of the pressure-dependent thermal unimolecular dissociation rates for the center dot QOOH intermediate-again increased by heavy- atom tunneling-which are required for global models of atmospheric and combustion chemistry.