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用ab initio分子轨道理论研究和确定氟化氢对乙烯分子型加成反应的可能途径.考虑了两种可能的反应机制。一为经过一个四中心过渡态的顺式加成;另一为经过一垂直过渡态(氟化氢分子轴垂直于C=C双键并在其中点的上方)。计算结果表明(STO-3G和4-31G),前者是可能的反应途径。计算的活化能是58.68kcal/mol(245.52kJ/mol),文献报道值是54±3kcal/mol(225.94±12.56kJ/mol)。分析和讨论了反应过程中Mulliken集居数的变化。比较了过渡态附近该“给一受络合物”中电子得失情况的变化,并用前线轨道理论作了解释。根据反应过程中氟化氢的“非键对”参与情况,说明该顺式四中心加成途径不在Woodward-Hoffmann规则禁阻之列。
The ab initio molecular orbital theory is used to study and determine the possible ways for the addition of hydrogen fluoride to the ethylene molecule. Two possible reaction mechanisms are considered. One is a cis-addition through a four-center transitional state and the other is through a vertical transitional state (the molecular axis of hydrogen fluoride is perpendicular to the C = C double bond and above its midpoint). The results show that (STO-3G and 4-31G), the former is a possible reaction pathway. The calculated activation energy is 58.68 kcal / mol (245.52 kJ / mol), reported in the literature is 54 ± 3 kcal / mol (225.94 ± 12.56 kJ / mol). The changes of Mulliken population during the reaction were analyzed and discussed. The changes of the electronic gain and loss in this “to one-acceptor complex” near the transition state were compared and explained by the frontier orbital theory. According to the “non-key pair” participation of hydrogen fluoride during the reaction, the cis-4-center addition route is not listed in the Woodward-Hoffmann rule.