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用量子化学从头计算方法研究了2-羟基-1-氧基乙烯自由基的质子转移反应。首先,在UHF/3-21G的水平上,采用能量梯度法优化了反应物和过渡态的几何构型,然后利用这两个优化的构型做了振动分析,找出相应的振动频率和模式,从而得到质子转移反应的活化熵值。此外,又做了内禀反应坐标途径(IRC)。为了求得比较准确的反应势能剖面,以便进行隧道效应校正,用多体微扰法(二级微扰)同时在参加转移的氢原子上附加了扩散函数p(UMP_2/3-21G~+)在IRC的各点上进行能量校正。根据从以上计算结果拟合的抛物线势,求出质子转移的隧道效应校正系数为19.9,然后由过渡状态理论计算了此反应的比速常数为7.4×10~(11)s~(-1)。此外,还得到了该自由基的分子内氢键键能和键长分别为19.2 kJ mol~(-1)和2.057(UMP_2/3-21G~+结果)。
The proton transfer reaction of 2-hydroxy-1-oxyethylene radical was studied by ab initio quantum chemistry method. First, at the level of UHF / 3-21G, the energy gradient method was used to optimize the geometry of the reactants and transition states. Then the vibration analysis was done with these two optimized configurations to find out the corresponding vibrational frequencies and modes , Thus obtaining the activation entropy of the proton transfer reaction. In addition, the intrinsic response coordinate pathway (IRC) was also done. In order to get a more accurate cross-section of potential energy for tunneling correction, the diffusion function p (UMP_2 / 3-21G ~ +) is added to the hydrogen atoms participating in the transfer simultaneously by the multi-body perturbation method (second order perturbation) Perform energy correction at each point of the IRC. Based on the parabolic potential fitted by the above calculation results, the tunneling correction factor for proton transfer was found to be 19.9, and then the specific rate constant for this reaction was calculated to be 7.4 × 10-11 s -1 by the transition state theory. . In addition, the intramolecular hydrogen bond bond energy and bond length of the free radical were obtained as 19.2 kJ mol -1 and 2.057 mol% (UMP_2 / 3-21G ~ +) respectively.