烷基苯酰胺缩合反应机理的量子化学研究

用量子化学方法研究了丙酸与苯胺缩合反应机理。并用ＭＮＤＯ方法进行了优化计算，得到了丙酸苯胺盐及其质子化的丙酸苯胺盐的平衡几何构型、净电荷和酸催化下的亲核加成及消除反应的势能曲线。由过渡态能量与基态能量之差求得这两个反应的活化能分别为３２．４８ｋＪ／ｍｏｌ和５８１．３２ｋＪ／ｍｏｌ．计算结果表明，消除反应是速度控制步骤。由计算结果发现，质子化后丙酸羰基碳原子上的净电荷增大，前线分子轨道的能级差比未质子化的能级差小得多，即质子化后前线分子轨道间更易相互作用。这表明酸催化大大增强了反应活性，酸催化的本质在理论上得以体现

QUANTUM CHEMISTRY APPLIED TO CONDENSATION MECHANISM ON ALKYL ARYLAMIDE

Quantum chemistry is applied to study condensation reaction mechanism of propionate acid and aniline. It is found that this activation increased remarkably by acid catalyst. Nucleophilic addition and elimination are considered as the key steps of this reaction, and the rate of reaction is determined by the latter. By using MNDO method, equilibrium geometries, net charges and the potential curves of the reaction are obtained. The activation energies calculated are 32.48 kJ/mol and 581.32 kJ/mol for the nucleophilic addition and elimination respectively. The results show that the protonation on O(3) atom led to an increase of charge on C(2), N atom and smaller gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. This suggests that the interaction between the frontier orbitals is easier after protonation. In the case, acid catalyst plays an important role for the reaction.