有机锡化合物催化合成碳酸二甲酯的密度泛函理论研究

Density Functional Study on Preparation of Dimethyl Carbonate Catalyzed by Organotin Compounds

采用DMol3密度泛函理论方法研究了二丁基二甲氧基锡催化氨基碳酸甲酯合成碳酸二甲酯的能量变化和电子性质.研究结果表明,在没有催化剂的作用下,氨基碳酸甲酯与甲醇反应的活化能为142.7 kJ/mol.在二丁基二甲氧基锡的催化作用下,氨基碳酸甲酯与甲醇的关键两步反应的活化能分别为107.1和77.0 kJ/mol.对部分化合物进行了自然键轨道(NBO)分析,计算结果表明,由于催化剂的参与,二丁基二甲氧基锡与氨基碳酸甲酯形成的中间物改变了氨基碳酸甲酯的电子性质,提高了羰基碳的正电性和氮的负电性,有利于羰基碳的亲电性和氮的亲核性,因而降低了反应的活化能.

The DMol3 calculations based on the density functional theory（DFT）,have been employed to investigate the energy change and electronic properties of synthesis of dimethyl carbonate from methyl carbamate catalyzed by dibutyldimethoxytin.The results show that activation energy of reaction between NH2COOCH3 and CH3OH is 142.7 kJ/mol in the absence of catalyst,while the activation energies of two key reactions catalyzed by dibutyldimethoxytin are 107.1 kJ/mol and 77.0 kJ/mol respectively.The analysis of natural bond orbital（NBO） was performed for CH3OH,NH2COOCH3 and（C4H9）2Sn（OCH3）NHCOOCH3.The calculation results demonstrate that the electronic properties are changed due to the intermediate formation between methyl carbamate and dibutyldimethoxyltin,the positive polarity of carbonyl carbon and negative polarity of nitrogen are enhanced.This is beneficial to electrophilic reactivity of carbonyl carbon and nucleophilic reactivity of nitrogen,resulting in the decrease of activation energy.