对苯二甲酸与乙二醇反应机理的量子化学研究

Quantum Chemistry Study on the Reaction Mechanism of Terephthalic and Ethylene Glycol

用从头算理论的Hartree-Fock（HF）方法，在3～21g基组水平上研究了以盐酸为催化剂对苯二甲酸与乙二醇反应的微观机理，优化了反应物、中间体、过渡态和产物的几何构型，并分别计算了它们的能量。振动分析结果证实了中间体和过渡态的正确性，内禀反应坐标（IRC）计算结果进一步确认了反应路径。在3—21g基组水平上计算了它们的能量。反应机理研究结果显示，对苯二甲酸与乙二醇反应过程可分为以下步骤①1A＋HCl→TSl→M1＋CI^-②M1＋2B→TS2→M2→TS3→M3＋H2O③M3＋Cl^-→TS4→M＋HCl。反应活化能分别为0．85kJ／mol；105．91kJ／mol；202．64kJ／mol；85．91kJ／mol。通过比较各步反应的活化能可以看出，反应通道M2→TS3→M3＋H2O的活化能最高，因此对苯二甲酸与乙二醇反应的速率是由本控制步骤决定的，这与实验结果相吻合。

Abstract： Ab initio Hartree-Fock（HF） method was performed to study the reaction mechanism of the reaction of terephthalic and ethylene glycol with hydrochloric acid as catalyst. The geometric configurations of reactants, intermediates, transition states and products were optimized by HF method at 3-21g level; moreover the energies of stationary points along the pathway were calculated. Intermediates and transition states were confirmed by the results of vibrational analysis. The pathway was calculated by IRC. From the results of the reaction mechanism of the reaction of terephthalic and ethylene glycol, lve can see that the reaction of terephthalic and ethylene glycol is as follows： ①IA＋ HCI→TSI→M1 ＋Cl^- ;②M1 ＋2B→TS2→M2→TS3→M3 ＋ H2O;③M3 ＋Cl^-→TS4→M＋ HCl. The activation energies of the reaction are 0.85kJ/mol; 105.91kJ/mol; 202.64kJ/mol;85.91kJ/mol respectively, which is in good agreement with experimental results.