对苯二甲酸乙二醇酯二聚体水/醇/氨解机理的理论研究

Theoretical study on hydrolysis/alcoholysis/ammonolysis mechanisms of ethylene terephthalate dimer

采用密度泛函理论B3P86/6-31++G(d,p)方法对对苯二甲酸乙二醇酯二聚体的水/醇/氨解反应机理进行了理论研究。设计了水/醇/氨降解过程的各种可能反应路径,对参与反应的各种中间体、过渡态及产物进行了几何结构优化和频率计算以获得热力学与动力学参数值,分析了对苯二甲酸乙二醇酯二聚体主链酯键中的酰氧键位置水/醇/氨降解的反应机理。结果表明,水/醇/氨解能够降低对苯二甲酸乙二醇酯二聚体主链酯键中的酰氧键裂解的反应活化能,使反应更易于进行,其中水解中主要基元反应步的反应能垒最高约为169.0 kJ/mol,氨解最低约为153.0 kJ/mol,其次是醇解约为155.0 kJ/mol。

The mechanisms for the hydrolysis/alcoholysis/ammonolysis reactions of ethylene terephthalate dimer was studied by using the density functional theory B3P86/6-31++G(d,p) method. The possible reaction paths in the hydrolysis/alcoholysis/ammonolysis degradation process were proposed. The geometric structures of various intermediates, transition states, and products involved in the reaction were optimized, and their frequencies were calculated to get the thermodynamic and kinetic parameters. The reaction mechanism for the hydrolysis/alcoholysis/ammonolysis degradation in the acyl-oxygen bond position in the backbone chain of ethylene terephthalate dimer was analyzed. The results indicated that the hydrolysis/alcoholysis/ammonolysis reactions reduced the activation energy of the acyl-oxygen bond cleavage in the main chain ester bond of ethylene terephthalate dimer, resulting in an easier reaction. The main element reaction in the hydrolysis had the highest energy barrier of 169. 0 kJ/mol, whereas the ammonolysis reaction had the lowest energy barrier of 153. 0 kJ/mol. The alcoholysis reaction exhibited an energy barrier of 155. 0 kJ/mol.