Isopropylcyclopropane + OH gas phase reaction: a quantum chemistry + CVT/SCT approach.
Isopropylcyclopropane + OH gas phase reaction: a quantum chemistry + CVT/SCT approach.
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DOI：
10.1021/jp056117x
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发表时间：
2006-01
期刊：
影响因子：
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通讯作者：
A. Galano;A. Cruz-Torres;J. R. Álvarez-Idaboy
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文献类型：
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作者：
A. Galano;A. Cruz-Torres;J. R. Álvarez-Idaboy
从理论上研究了异丙基环丙烷(IPCP)脱氢反应的机理和动力学。在BHandHLYP/6-311++G(d，p)理论水平上计算了所有驻点以及沿最小能量路径(MEP)的附加点的最佳几何构型、频率和梯度。用CCSD(T)/6-311++G(d，p)对上述几何构型进行了单点计算，得到了势能面。利用正则变分理论(CVT)和小曲率隧道效应(SCT)修正，计算了260-350K温度范围内的速率系数。我们的分析表明，对于所有模拟的路径，在入口通道中形成反应物络合物，在出口通道中形成产物络合物的分步机制。详细研究了反应物的络合物，因为它们具有类似烯烃的结构。298K时总的计算速率系数和实验速率系数之间的良好一致性支持了本文首次提出的IPCP+OH反应的温度依赖性参数和分支比参数的可靠性。最能描述所研究反应的表达式为：k(总体)=6.15×10(-13)e1747/RT cm~3 x分子(-1)x S(-1)。预测的活化能为-0.89千卡/摩尔。
A theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from isopropylcyclopropane (IPCP) is presented. Optimum geometries, frequencies and gradients have been computed at the BHandHLYP/6-311++G(d,p) level of theory for all stationary points, as well as for additional points along the minimum energy path (MEP). Energies have been improved by single-point calculations at the above geometries using CCSD(T)/6-311++G(d,p) to produce the potential energy surface. The rate coefficients are calculated for the temperature range 260-350 K by using canonical variational theory (CVT) with small-curvature tunneling (SCT) corrections. Our analysis suggests a stepwise mechanism involving the formation of a reactant complex in the entrance channel and a product complex in the exit channel, for all the modeled paths. The reactant complexes are examined in detail, because they exhibit alkene-like structure. The excellent agreement between the overall calculated and experimental rate coefficients at 298 K supports the reliability of the parameters obtained for the temperature dependence and branching ratios of the IPCP + OH reaction, proposed here for the fist time. The expression that best describes the studied reaction is k(overall) = 6.15 x 10(-13)e1747/RT cm3 x molecule(-1) x s(-1). The predicted activation energy is -0.89 kcal/mol.