苯胺与乙酸酐反应机理及溶剂化效应的理论研讨.pdfVIP

苯胺与乙酸酐反应机理及溶剂化效应的理论研究 龙清平 纪红兵*， 中山大学化学与化工学院，广州，510275，cehbji@scut.edu.cn 摘要 用量子化学密度泛函理论(DFT)研究苯胺与乙酸酐的乙酰化反应。在B3LYP/6- 31G (d)水平 上全优化计算了反应物、产物、中间体和过渡态的几何构型、振动频率和零点能。采用 B3LYP/6-311G (d, p) 方法计算各驻点更精确的单点能，并对其能量进行零点能校正。在 B3LYP/6-31G(d)水平上进行内禀坐标(IRC)计算和频率分析, 确认了过渡态的真实性。通过自洽 反应场(SCRF)的Onsager模型，在B3LYP/6-31G(d)水平上考察溶剂水(相对介电常数ε=78.39)对苯 胺与乙酸酐反应势能面上各驻点的结构和反应机理的影响。计算结果表明，苯胺的乙酰化反应 是可通过两条反应路径进行，Path1经过3个过渡态(TS)和2个中间体(IM)的三步反应过程，Path2 经过2个过渡态(TS)和1个中间体(IM) 的两步反应过程，均属于加成-消去反应机理，加成基元反 应的势垒较大，是反应的速控步，内旋转过程势垒很小，消去基元步的势垒较小。水的溶剂化 效应使R 15 -21和R 15 -21缩短，有利于两反应物分子靠近发生作用，从而降低决速步的反应势垒， 且由于消去基元反应Ⅱ的活化能降低较多，使得反应较气相中更易沿Path2进行。 关键词 苯胺，乙酸酐，密度泛函理论，反应机理，溶剂效应 Theoretical Study on Reaction Mechanism and Solvent effect ofAniline with Acetic Anhydride Long Qingping ，Ji Hongbing The school of chemistry and chemical engineer, Sun Yat-Sen University, GuangZhou, 510275, cehbji@scut.edu.cn Abstract The reaction between aniline and acetic anhydride has been studied by means of the density functional theory (DFT) method. The geometries, vibrational frequencies and zero point energy for the reactants, products, intermediates and transition states have been completely optimized at the computational level of B3LYP/6-31G(d), and single point energies of these species were calculated by more accurate method of B3LYP/6-311G(d, p). All the transition states have been verified by the vibrational analysis and internal reaction coordinate (IRC) calculations. Combined self-consistent reaction field (SCRF) with Onsager model, the solvent effects of H2O (ε=78.39) on the geometries and the reaction mechanism have been studied by B3LYP/6-31G (d). The calculated results show that the reaction between aniline and acetic anhydride belongs to addition elimination reactions.