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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Variational analysis of the phenyl + O-2 and phenoxy plus O reactions
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Variational analysis of the phenyl + O-2 and phenoxy plus O reactions

机译：苯基+ O-2与苯氧基加O反应的变异分析

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Variational transition state analysis was performed on the barrierless phenyl + O-2 and phenoxy + O association reactions. In addition, we also calculated rate constants for the related vinyl radical (C2H3) + O-2 and vinoxy radical (C2H3O) + O reactions and provided rate constant estimates for analogous reactions in substituted aromatic systems. Potential energy scans along the dissociating C-OO and CO-O bonds (with consideration of C-OO internal rotation) were obtained at the O3LYP/6-31G(d) density functional theory level. The CO-O and C-OO bond scission reactions were observed to be barrierless, in both phenyl and vinyl systems. Potential energy wells were scaled by G3B3 reaction enthalpies to obtain accurate activation enthalpies. Frequency calculations were performed for all reactants and products and at points along the potential energy surfaces, allowing us to evaluate thermochemical properties as a function of temperature according to the principles of statistical mechanics and the rigid rotor harmonic oscillator (RRHO) approximation. The low-frequency vibrational modes corresponding to R-OO internal rotation were omitted from the RRHO analysis and replaced with a hindered internal rotor analysis using O3LYP/6-31 G(d) rotor potentials. Rate constants were calculated as a function of temperature (300-2000 K) and position from activation entropies and enthalpies, according to canonical transition state theory; these rate constants were minimized with respect to position to obtain variational rate constants as a function of temperature. For the phenyl + O-2 reaction, we identified the transition state to be located at a C-OO bond length of between 2.56 and 2.16 angstrom (300-2000 K), while for the phenoxy + O reaction, the transition state was located at a CO-O bond length of 2.00-1.90 angstrom. Variational rate constants were fit to a three-parameter form of the Arrhenius equation, and for the phenyl + O-2 association reaction, we found k(T) 1.860 x 10(13)T(-0.217) exp(0.358/7) (with k in cm(3) mol(-1) s(-1) and T in K); this rate equation provides good agreement with low-temperature experimental measurements of the phenyl + O-2 rate constant. Preliminary results were presented for a correlation between activation energy (or reaction enthalpy) and pre-exponential factor for heterolytic O-O bond scission reactions.
机译：对无障碍苯基+ O-2和苯氧基+ O缔合反应进行了变分过渡态分析。此外，我们还计算了相关的乙烯基自由基（C2H3）+ O-2和乙烯基氧基（C2H3O）+ O反应的速率常数，并提供了取代芳族体系中类似反应的速率常数估算值。在O3LYP / 6-31G（d）密度泛函理论水平上获得了沿解离的C-OO和CO-O键的势能扫描（考虑了C-OO内部旋转）。在苯基和乙烯基体系中，观察到CO-O和C-OO键断裂反应是无障碍的。通过G3B3反应焓来缩放势能阱，以获得准确的活化焓。对所有反应物和产物以及沿势能面的各个点进行了频率计算，从而使我们能够根据统计力学原理和刚性转子谐波振荡器（RRHO）近似来评估热化学性质随温度的变化。 RRHO分析中省略了与R-OO内部旋转相对应的低频振动模式，并使用O3LYP / 6-31 G（d）转子电势代替了受阻内部转子分析。根据规范的过渡态理论，根据活化熵和焓，将速率常数计算为温度（300-2000 K）和位置的函数;这些速率常数相对于位置最小化，以获得随温度变化的速率常数。对于苯基+ O-2反应，我们确定过渡态位于2.56和2.16埃（300-2000 K）之间的C-OO键长，而对于苯氧基+ O反应，过渡态位于CO-O键长度为2.00-1.90埃。变化率常数适合Arrhenius方程的三参数形式，对于苯基+ O-2缔合反应，我们发现k（T）1.860 x 10（13）T（-0.217）exp（0.358 / 7） （k以cm（3）mol（-1）s（-1）为单位，T以K为单位）;该速率方程与低温实验中苯基+ O-2速率常数的实验结果吻合良好。初步结果表明了杂化O-O键断裂反应的活化能（或反应焓）和指数前因子之间的相关性。

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