Phenolic Hydrogen Transfer by Molecular Oxygen and Hydroperoxyl Radicals. Insights into the Mechanism of the Anthraquinone Process
Phenolic Hydrogen Transfer by Molecular Oxygen and Hydroperoxyl Radicals. Insights into the Mechanism of the Anthraquinone Process
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DOI：
10.1021/acs.joc.9b03286
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发表时间：
2020-02-21
影响因子：
3.6
通讯作者：
Mulder, Peter
中科院分区：
文献类型：
--
作者：
Korth, Hans-Gert;Mulder, Peter
用CBS-QB 3方法研究了O-3（2）和HO 2中心点从芳香醇（ArOH）、芳氧基（ArO中心点）、它们的互变异构体（ArH）和辅助化合物中的氢原子转移（HAT）.在O-3（2）的情况下，发现活化焓与总反应焓之间存在良好的线性相关性。不同的途径已被识别为涉及OH或CH部分的HAT。ArOH + HO_2中心点-> ArO中心点+H_2O_2的实验结果与实验值不符合，也不存在线性关系。蒽氢醌（AnH（2）Q）液相自氧化的精确机理似乎尚未完全了解。动力学分析表明，HAT由链携带HO 2中心点发生，具有>= 6 × 10（8）M-1 s（-1）（甲苯）的高速率常数。第二个增长步骤涉及由10-OH-9-anthroxyl自由基的O-3（2）进行的扩散控制的HAT。氧蒽酮（AnOH）是AnH（2）Q在非氢键（HB）溶剂中的一种较稳定的互变异构体，其比例为13（298 K），但对O-3（2）/HO 2中心点的反应活性较低。计算的自由能和Abrahams的HB给予（alpha（H）（2））和接受（beta（H）（2））参数的组合提供了0.86的alpha（H）（2）（HO 2中心点）和0.50的alpha（H）（2）（H2 O2）。
Hydrogen atom transfer (HAT) by O-3(2) and HO2 center dot from arenols (ArOH), aryloxyls (ArO center dot), their tautomers (ArH), and auxiliary compounds has been investigated by means of CBS-QB3 computations. With O-3(2), excellent linear correlations have been found between the activation enthalpy and the overall reaction enthalpy. Different pathways have been discerned for HATs involving OH or CH moieties. The results for ArOH + HO2 center dot -> ArO center dot + H2O2 neither afford a linear correlation nor agree with the experiment. The precise mechanism for the liquid-phase autoxidation of anthrahydroquinone (AnH(2)Q) appears to be not fully understood. A kinetic analysis shows that the HAT by chain-carrying HO2 center dot occurs with a high rate constant of >= 6 x 10(8) M-1 s(-1) (toluene). The second propagation step pertains to a diffusion-controlled HAT by O-3(2) from the 10-OH-9-anthroxyl radical. Oxanthrone (AnOH) is a more stable tautomer of AnH(2)Q with a ratio of 13 (298 K) in non-hydrogen-bonding (HB) solvents, but the reactivity toward O-3(2)/HO2 center dot is much lower. Combination of the computed free energies and Abrahams' HB donating (alpha(H)(2)) and accepting (beta(H)(2)) parameters has afforded an alpha(H)(2)(HO2 center dot) of 0.86 and an alpha(H)(2)(H2O2) of 0.50.