Mechanism of the aminolysis of methyl benzoate: A computational study
Mechanism of the aminolysis of methyl benzoate: A computational study
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DOI：
10.1021/jp0536403
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发表时间：
2005-12-22
影响因子：
2.9
通讯作者：
Schaefer, HF III
中科院分区：
文献类型：
--
作者：
Galabov, B;Atanasov, Y;Schaefer, HF III
采用密度泛函和从头算方法研究了苯甲酸甲酯与氨反应的可能机理。确定了协调和中性逐步机制的过渡态结构和能量。理论计算结果表明，这两种可能的反应途径具有相似的活化能。还考察了该过程的一般碱催化作用。预测结果表明，该催化过程的结果在相当大的能量节省和最有利的反应途径是通过一般碱催化的中性逐步机制。过渡态的结构和跃迁矢量表明氨的催化作用是通过促进质子转移过程实现的。对苯甲酸甲酯和甲酸甲酯氨解反应的热力学进行了比较，结果表明脂肪酸酯的氨解反应更为有利。这两种酯的不同反应性解释在酯官能度的原子处的静电势值方面。
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.