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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical study of the oxidation reactions of methylacrylic acid and methyl methacrylate by triplet O-2
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Theoretical study of the oxidation reactions of methylacrylic acid and methyl methacrylate by triplet O-2

机译：三重态O-2氧化甲基丙烯酸和甲基丙烯酸甲酯的反应的理论研究

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摘要

The oxidations of organic compounds and polymers by triplet O-2 were called "dark oxidation" or "auto-oxidation", in contrast to their "photo-oxidation" by singlet O-2. To study the relevant dark oxidation mechanism we take methylacrylic acid (MAA) and methyl methacrylate (MMA) as prototypes to study their reactions with triplet O-2 by performing density functional theory calculations. Two reaction channels, the C-H bond oxidation and CC bond oxidation, have been characterized in detail. The structures of the initial contact charge-transfer complexes, intermediates, transition states, and final oxides involved in the reactions have been localized at the UB3LYP/6-311+G(d,p) level. It is found that the C-H bond in the methyl group connected to the CC bond presents relatively higher reactivity toward triplet O-2 than the CC bond itself. Thus, the reactions are expected to proceed via the C-H bond oxidation branch at room temperature and also via CC bond oxidation at elevated temperature. In this sense, an effective method for preventing or retarding the dark oxidations of MAA and MMA in a natural environment is to chemically decorate or protect the C-H bond in the methyl connected to the CC bond. The present results are expected to provide a general guide for understanding the dark oxidation mechanism of organic compounds and polymers.
机译：三重态O-2对有机化合物和聚合物的氧化称为“暗氧化”或“自氧化”，而单重态O-2对有机化合物和聚合物的“光氧化”则相反。为了研究相关的暗氧化机理，我们以甲基丙烯酸（MAA）和甲基丙烯酸甲酯（MMA）为原型，通过执行密度泛函理论计算研究了它们与三重态O-2的反应。已经详细描述了两个反应通道，即C-H键氧化和CC键氧化。反应中涉及的初始接触电荷转移络合物，中间体，过渡态和最终氧化物的结构已被定位在UB3LYP / 6-311 + G（d，p）水平。发现与CC键连接的甲基中的C-H键对三重态O-2的反应性比CC键本身更高。因此，预期反应在室温下通过C-H键氧化分支进行，并且在高温下也通过CC键氧化进行。从这个意义上说，在自然环境中防止或延迟MAA和MMA暗氧化的有效方法是化学修饰或保护连接CC键的甲基中的C-H键。预期本结果将为理解有机化合物和聚合物的暗氧化机理提供一般指导。

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