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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Atmospheric Oxidation Mechanism of Toluene
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Atmospheric Oxidation Mechanism of Toluene

机译：甲苯的大气氧化机理

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The atmospheric oxidation mechanism of toluene initiated by OH radical addition is investigated by quantum chemistry calculations at M06-2X, G3MP2-RAD, and ROCBS-QB3 levels and by kinetics calculation by using transition state theory and unimolecular reaction theory coupled with master equation (RRKM-ME). The predicted branching ratios are 0.15, 0.59, 0.05, and 0.14 for OH additions to ipso, ortho, meta, and para positions (forming R1?R4 adducts), respectively. The fate of R2, R4, and R1 is investigated in detail. In the atmosphere, R2 reacts with O_2 either by irreversible H-abstraction to form o-cresol (36%), or by reversible recombination to R2-1OO-syn and R2-3OO-syn, which subsequently cyclize to bicyclic radical R2-13OOsyn (64%). Similarly, R4 reacts with O_2 with branching ratios of 61% for p-cresol and 39% for R4-35OO-syn, while reaction of R1 and O_2 leads to R1-26OO-syn. RRKM-ME calculations show that the reactions of R2/R4 with O_2 have reached their highpressure limits at 760 Torr and the formation of R2-16O-3O-s is only important at low pressure, i.e., 5.4% at 100 Torr. The bicyclic radicals (R2-13OO-syn, R4-35OO-syn, and R1-26OO-syn) will recombine with O_2 to produce bicyclic alkoxy radicals after reacting with NO. The bicyclic alkoxy radicals would break the ring to form products methylglyoxal/glyoxal (MGLY/GLY) and their corresponding coproducts butenedial/methyl-substituted butenedial as proposed in earlier studies. However, a new reaction pathway is found for the bicyclic alkoxy radicals, leading to products MGLY/GLY and 2,3-epoxybutandial/2-methyl-2,3- epoxybutandial. A new mechanism is proposed for the atmospheric oxidation mechanism of toluene based on current theoretical and previous theoretical and experimental results. The new mechanism predicts much lower yield of GLY and much higher yield of butenedial than other atmospheric models and recent experimental measurements. The new mechanism calls for detection of proposed products 2,3-epoxybutandial and 2-methyl-2,3-epoxybutandial.
机译：通过在M06-2X，G3MP2-RAD和ROCBS-QB3水平上的量子化学计算以及过渡态理论和单分子反应理论以及主方程（RRKM）的动力学计算，研究了由OH自由基加成引发的甲苯的大气氧化机理。 -我）。对于在ipso，邻位，间位和对位（形成R1？R4加合物）的OH加成，预测的支化比分别为0.15、0.59、0.05和0.14。详细研究了R2，R4和R1的命运。在大气中，R2通过不可逆的H吸收与O_2反应生成邻甲酚（36％），或通过可逆重组为R2-1OO-syn和R2-3OO-syn，随后环化为双环自由基R2-13OOsyn （64％）。同样，R4与O_2反应，对甲酚的支化率为61％，R4-3500O-syn的支化率为39％，而R1与O_2的反应生成R1-2600O-syn。 RRKM-ME计算表明，R2 / R4与O_2的反应在760 Torr时已达到高压极限，R2-16O-3O-s的形成仅在低压下很重要，即在100 Torr时为5.4％。双环基团（R21300-syn，R4-3500-syn和R1-2600-syn）在与NO反应后会与O_2结合生成双环烷氧基。如较早的研究中所提出的那样，双环烷氧基自由基将环断裂形成甲基乙二醛/乙二醛（MGLY / GLY）及其相应的副产物丁烯二醛/甲基取代的丁烯二醛。然而，发现了双环烷氧基的新反应途径，导致产物MGLY / GLY和2,3-环氧丁醛/ 2-甲基-2,3-环氧丁醛。根据目前的理论和以往的理论和实验结果，提出了一种新的甲苯大气氧化机理。与其他大气模型和最新的实验测量结果相比，这种新的机理预测出GLY的产率要低得多，butenedial的产率要更高。新机制要求检测拟议的产品2,3-环氧丁醛和2-甲基-2,3-环氧丁醛。

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