8-喹啉磺酸乙酯、异丙酯的气相热解反应

THEORETICAL STUDY ON MECHANISM OF THE GAS-PHASE PYROL YTIC REACTION OF ETHYL-2-QUINOLINE SULFONATE AND LSOPROPYL-2-QUINOLINE SULFONATE

采用PM3半经验方法和从头算密度泛函方法(B3LYP)研究了8-喹啉磺酸乙酯、异丙酯的气相热解反应机理,结果表明,此类反应经历两个基元反应步骤,第一步反应是通过一个紧密离子对过渡态的非同步的协同反应过程,其中乙基和异丙基碳正离子中的β-H原子帮助碳正离子和磺酸负离子的分离,C-O键的断裂是决定此反应的反应速度的关键。生成的8-喹啉磺酸继续进行分子内的酸碱中和反应。在B3LYP/6-311+G(2d,p)水平计算所得反应活化能分别为151.2 kJ.mol-1、137.9 kJ.mol-1,与相应的实验值相一致。

The gas -phase pyrolytic reactions of ethyl -8 -quinoline sulfonate and isopropyl -8 -quinoline sulfonate have been investigated by semi -empirical method PM3 and density functional theory （DFF） method. The resuits obtained show that the gas - phase pyrolytic reactions of ethyl - 8 - quinoline sulfonate and isopropyl - 8 - quinoline sulfonate process two steps：the first step occurs via an intimate ion -pair transition state, where the β- hydrogen atom of ethyl or isopropyl carbocation facilitates C - O bond cleavage, and the cleavage of C - O bond is rate determining. The generated 2 - pyridine sulfonic acid processes intramolecular acid - base neutralization. Corrected by zero - point energy, the activation energy obtained at B3 LYP/6 - 311 ＋ G （ 2d, p） level was 151.21 kJ ·mol^-1 ,131.9kJ · mol^-1 ,respectively.which are in accordance with the available experimental data.