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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ozonolysis Reactions of Monoterpenes: A Variational Transition State Investigation.
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Ozonolysis Reactions of Monoterpenes: A Variational Transition State Investigation.

机译：单萜的臭氧分解反应：变迁过渡态研究。

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The O-3-initiated oxidation reactions of a-pinene ([1S,5S]-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene), beta-pinene ([1R,5R]-6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane), camphene ([1R,4S]-2,2-dimethyl-3-methylenebicyclo[2.2.1]heptane) and sabinene ([1R,5R]-4-methylene-1-(1-methylethyl)bicycle[3.1.0]hexane), four monoterpenes typically emitted into the atmosphere, were studied at the B3LYP/6-31+G(2d,2p) level of theory. The rate coefficients were calculated on the basis of the variational transition state theory for two kinetic models, in order to investigate the reaction mechanism: first assuming a direct bimolecular reaction and the second, assuming the formation of a prebarrier-complex, which further reacts forming the corresponding molozonide. The barrier heights leading to the formation of exo-conformers of the molozonides of alpha-pinene and camphene are lower than the barrier heights for the formation of the endo-conformers of these molozonides, whereas the inverse trend is observed for beta-pinene and sabinene. The canonical variational rate coefficients are found in reasonable agreement with the experimental data, especially when the prebarrier complexes are considered. Microcanonical variational rate coefficients are also calculated, as a final validation test, being found in an expected agreement with the canonical rate coefficients. The best predictions for the rate coefficients at 298 K, based on the microcanonical variational method, for a-pinene, beta-pinene, camphene, and sabine are (in units cm(3) molecule(-1) s(-1)): 6.92 X 10(-17), 1.06 X 10(-17), 4.61 X 10(-19), and 4.81 X 10(-17), respectively. Our results suggest that the prebarrier complex is an important specie in the ozone addition mechanism and should be taken into account for the proper description of the overall kinetics.
机译：α-pine烯（[1S，5S] -2,6,6-三甲基双环[3.1.1]庚-2-烯），β-pine烯（[1R，5R] -6， 6-二甲基-2-亚甲基双环[3.1.1]庚烷），camp烯（[1R，4S] -2,2-二甲基-3-亚甲基双环[2.2.1]庚烷）和sa烯（[1R，5R] -4-在B3LYP / 6-31 + G（2d，2p）的理论水平上研究了通常排放到大气中的四个单萜亚甲基-1-（1-甲基乙基）二环[3.1.0]己烷）。为了研究反应机理，基于变分跃迁状态理论针对两个动力学模型计算了速率系数：第一个假设为直接双分子反应，第二个为形成预屏障复合物，并进一步发生反应。相应的莫洛宗尼德。导致形成α-pine烯和camp烯的间苯二酚外型构象的势垒高度低于形成这些these酮的内构异构体的势垒高度，而β-beta烯和ne烯的趋势却相反。发现规范变率系数与实验数据合理吻合，尤其是考虑到预屏障复合物时。还计算微规范变化率系数，作为最终验证测试，与规范率系数符合预期。基于微规范变分方法，对于α-pine烯，β-pine烯，樟脑和萨宾碱，速率系数在298 K时的最佳预测为（单位cm（3）分子（-1）s（-1） ：分别为6.92 X 10（-17），1.06 X 10（-17），4.61 X 10（-19）和4.81 X 10（-17）。我们的结果表明，预屏障配合物是臭氧添加机制中的重要物种，应适当考虑整体动力学。

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