物理化学学报 >> 1989, Vol. 5 >> Issue (06): 705-711.doi: 10.3866/PKU.WHXB19890612

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2-羟基-1-氧基乙烯自由基(C2H3O2)的分子内质子转移反应的理论研究

方德彩; 傅孝愿   

  1. 北京师范大学化学系
  • 收稿日期:1988-09-20 修回日期:1989-06-24 发布日期:1989-12-15
  • 通讯作者: 傅孝愿

A THEORETICAL STUDY ON THE INTRAMOLECULAR PROTON TRANSFER OF 2-HYDROXYETHENYL-1-OXYL

Fang Decai; Fu Xiaoyuan   

  1. Chemistry Department; Beijing Normal University
  • Received:1988-09-20 Revised:1989-06-24 Published:1989-12-15
  • Contact: Fu Xiaoyuan

摘要: 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0.2057 nm(UMP_2/3-21G~+结果)。

Abstract: Ab initio quantum chemical method has been used to study the proton transfer of the L-form of 2-hydroxyethenyl-1-oxy(C_2H_3O_2) radical. The geometries of the C_2H_3O_2 radical as well as the transition State of proton transfer have been optimized at the level of UHF/3-21G. Vibrational analysis has been made of tnese two configurations to obtain the vibrational frequencies, by means of which the entropy of activation of the proton transfer reaction of C_2H_3O_2 radical has been evaluated.
In order to get better energetics, the energies of some points on the Intrinsic Reation Corrdinate (based on the geometries of UHF/3-21G) have been recalculated at the level of UMP2/3-21G~+ (diffusion function has been added to the H atom participating the transfer). Potential energy profile and tunnel effect correction were obtained by using this proton transfer reaction was calculated to be 7.4×10~(11) s~(-1).
The intramolecular hydrogen bond stabilization energy and H-bond length H(1)O(5) obtained at the optimized geometries of UMP2/3-21G~+ are 19.2 kJ mol~(-1) and 0.2057 nm respectively.