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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Study on the Reaction Path and Variational Rate Constant of the Reaction HNCO + NH → NCO + NH_2
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Theoretical Study on the Reaction Path and Variational Rate Constant of the Reaction HNCO + NH → NCO + NH_2

机译：HNCO + NH→NCO + NH_2的反应路径及变化速率常数的理论研究

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The hydrogen abstraction reaction HNCO + NH → NCO + NH_2 has been studied using ab initio molecular orbital theory. The geometries of the reactants, hydrogen-bonded complex, transition state, and products have been optimized at the UMP2/6-311G~(**) level of theory. The forward and reverse reaction potential barriers calculated accurately at the UQCISD(T)/6-311G~(**) level of theory are 25.80 and 2.39 kcal/mol, respectively, and the heat of reaction is 20.32 kcal/mol. The minimum-energy path was calculated by the intrinsic reaction coordinate theory (IRC) at the UMP2/6-311G~(**) level with a gradient step size of 0.05 (amu)~(1/2) a_0. The changes of the geometries and normal-mode vibrational frequencies along the IRC were discussed. The energy profile along the IRC was refined by the UMP4/6-311G~(**) and UQCISD(T)/6-311G~(**) single-point energy calculations. The forward and the reverse reaction rate constants for the temperature range 1000-3000 K were obtained by the variational transition-state theory. The theoretical rate constants of the forward reaction re 2.7, 10.2 and 20.5 times the experimental rate constants at the temperatures 1000, 2000, and 3000 K, respectively. The reverse reaction rate constants are at least an order of magnitude greater than the forward reaction rate constants.
机译：利用从头算分子轨道理论研究了氢提取反应HNCO + NH→NCO + NH_2。在UMP2 / 6-311G〜（**）的理论水平上，已优化了反应物的几何形状，氢键配合物，过渡态和产物。在UQCISD（T）/ 6-311G〜（**）的理论水平上精确计算出的正向和逆向反应势垒分别为25.80和2.39 kcal / mol，反应热为20.32 kcal / mol。通过内在反应坐标理论（IRC）在UMP2 / 6-311G〜（**）水平上计算出最小能量路径，梯度步长为0.05（amu）〜（1/2）a_0。讨论了沿IRC的几何形状和正常模式振动频率的变化。沿IRC的能量分布通过UMP4 / 6-311G〜（**）和UQCISD（T）/ 6-311G〜（**）单点能量计算得到了完善。通过变分过渡态理论获得了温度范围为1000-3000 K时的正反反应速率常数。在1000、2000和3000 K的温度下，正向反应的理论速率常数分别是实验速率常数的2.7、10.2和20.5倍。反向反应速率常数至少比正向反应速率常数大一个数量级。

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