苍术酮氧化机理的密度泛函研究

Density functional theory study of atractylon oxidation mechanism

在298.15 K和101.325 kPa条件下,根据密度泛函理论,使用Gaussian03程序,在B3LYP/6-31G水平上,以实验上所检测到的白术内酯Ⅰ、表白术内酯Ⅰ、白术内酯Ⅱ、白术内酯Ⅲ和双白术内酯为设计反应路径的出发点,详细研究苍术酮氧化反应的机理。在拟定反应机理的基础上,获得了14个稳定构型和13个过渡态,优化构型表明五元环为白术的官能团,五元环经历了开环,闭环的过程——从平面结构到扭曲再到平面结构,证明苍术酮在氧化过程中有2条反应通道:通道1生成白术内酯Ⅰ,通道2生成表白术内酯Ⅰ。并计算了各反应路径的热力学和动力学参数,结果说明苍术酮与水的加成反应,是整个反应过程的速度控制步骤,活化能分别为223.25 kJ/mol和216.75 kJ/mol,且前者为吸热过程,后者为放热过程。计算结果确认了实验上已检测的物质,并从理论上预测了可能存在的氧化物质。苍术酮的氧化机理对研究白术的炮制及提纯具有重要意义。

To investigate the detected atractylenolideⅠ,iso-atractylenolideⅠ,atractylenolideⅡ,atractylenolideⅢand biatractylenolide,reaction path for the design of the starting point,in the ideal gas state at 298.15 K and 101.325 KPa,the atractylon oxidation reaction mechanism was studied in detail at the B3LYP/6-31G level with Gaussian03.In the formulation based on the reaction mechanism,14 Structural Stabilities and 13 transition states were obtained.Optimized geometries showed that the five-membered ring of atractylon functional groups,which have undergone open-loop, closed-loop process,from flat structure to distort the planar structure.And then two reaction channels were proved in the course of atractylon：channel one generated atractylenolideⅠ;while channel two generated iso-atractylenolideⅠ.The results calculated the thermodynamic and kinetic parameters of the reaction channels showed that the reaction process of atractylon with the addition of water was the rate controlling step,Activation energies were 223.25 kJ / mol and 216.75 kJ / mol,respectively.And the former was an endothermic process,latter was exothermic.The substances detected experimentally and predicted oxidation material in the possible existence were confirmed.Atractylon oxidation mechanism is great important in its processing and purification.