物理化学学报 >> 2003, Vol. 19 >> Issue (05): 389-392.doi: 10.3866/PKU.WHXB20030502

研究论文 上一篇    下一篇

2-溴丙酸气相热消除反应的机理

李永红;陈丽萍;徐文媛;洪三国   

  1. 江西师范大学化学学院, 南昌 330027
  • 收稿日期:2002-07-04 修回日期:2002-10-11 发布日期:2003-05-15
  • 通讯作者: 洪三国 E-mail:hsg@ncu.edu.cn

Reaction Mechanism of the Gas-phase Elimination of 2-bromopropionic Acid

Li Yong-Hong;Chen Li-Ping;Xu Wen-Yuan;Hong San-Guo   

  1. Department of Chemistry, Jiangxi Normal University, Nanchang 330027
  • Received:2002-07-04 Revised:2002-10-11 Published:2003-05-15
  • Contact: Hong San-Guo E-mail:hsg@ncu.edu.cn

摘要: 用密度泛函(DFT)方法,在B3LYP/6-31G**水平上对2-溴丙酸气相消除反应机理进行了研究.计算表明,反应主要是通过半极化五元环结构过渡态进行的,羧基上的氢原子协助溴原子离去,羧基氧原子帮助稳定过渡态.在B3LYP/6-311++G(3df,3pd)水平上对B3LYP/6-31G**优化的几何构型进行了单点能计算,计算所得反应的速度控制步骤的活化能为189.461 kJ•mol-1,偏离实验值((180.3±3.4) kJ•mol-1)5.08%.

关键词: 2-溴丙酸, 气相消除反应, 密度泛函理论(DFT), 反应机理

Abstract: The gas-phase elimination of 2-bromopropionic acid was investigated using density functional theory (DFT) method. Molecular structures were calculated at the B3LYP/6-31G** level. The results obtained show that the gas-phase elimination of 2-bromopropionic acid proceeds via a semi-polar five-membered cyclic transition state, where the acidic H of the group COOH assisted the leaving Br atom, and the carboxylic oxygen stabilized this transition state. The single-point energies of all optimized molecular structures by B3LYP/6-31G** were counted at B3LYP/6-311++G (3df,3pd) level. The activation energy(Ea1=ETS1-ERe)of the rate-controlling step obtained at B3LYP/6-311++G (3df,3pd) level was 189.5 kJ•mol-1,which is closely correlated with the available experimental data(180.3±3.4) kJ•mol-1.The relative error is 5.08%.

Key words: 2-bromopropionic acid, Gas-phase elimination, Density functional theory(DFT), Reaction mechanism