Galabov Boris, Atanasov Yasen, Ilieva Sonia, Schaefer Henry F
Department of Chemistry, University of Sofia, Sofia 1164, Bulgaria.
J Phys Chem A. 2005 Dec 22;109(50):11470-4. doi: 10.1021/jp0536403.
Density functional and ab initio methods were applied in examining the possible mechanistic pathways for the reaction of methyl benzoate with ammonia. Transition state structures and energies were determined for concerted and neutral stepwise mechanisms. The theoretical results show that the two possible pathways have similar activation energies. The general base catalysis of the process was also examined. The predictions reveal that the catalytic process results in considerable energy savings and the most favorable pathway of the reaction is through a general-base-catalyzed neutral stepwise mechanism. The structure and transition vectors of the transition states indicate that the catalytic role of ammonia is realized by facilitating the proton-transfer processes. Comparison of the energetics of the aminolysis for methyl benzoate and methyl formate shows the more favorable process to be that for the aliphatic ester. The differing reactivity of the two esters is explained in terms of the electrostatic potential values at the atoms of the ester functionality.
采用密度泛函和从头算方法研究苯甲酸甲酯与氨反应可能的机理途径。确定了协同和中性逐步机理的过渡态结构和能量。理论结果表明，两条可能的途径具有相似的活化能。还研究了该过程的一般碱催化作用。预测结果表明，催化过程可显著节省能量，且反应最有利的途径是通过一般碱催化的中性逐步机理。过渡态的结构和过渡向量表明，氨的催化作用是通过促进质子转移过程来实现的。苯甲酸甲酯和甲酸甲酯氨解反应能量学的比较表明，脂肪族酯的反应过程更有利。根据酯官能团原子处的静电势值解释了两种酯不同的反应活性。
