物理化学学报 >> 1997, Vol. 13 >> Issue (10): 908-915.doi: 10.3866/PKU.WHXB19971009

研究论文 上一篇    下一篇

氯代酸气相热消除反应的理论研究

宋维平,傅孝愿,何绍仁   

  1. 北京师范大学化学系,北京 100875
  • 收稿日期:1997-01-31 修回日期:1997-05-07 发布日期:1997-10-15
  • 通讯作者: 傅孝愿

Theoretical Studies on the Mechanism of Chloro-carboxylic Acids Gas-phase Elimination Process

Song Wei-Ping,Fu Xiao-Yuan,He Shao-Ren   

  1. Department of Chemistry,Beijing Normal University,Beijing 100875
  • Received:1997-01-31 Revised:1997-05-07 Published:1997-10-15
  • Contact: Fu Xiao-Yuan

摘要:

应用半经验分子轨道AM1法,辅以Berny梯度优化法对3-氯丙酸和2-氯丁酸在气相中的热消除反应进行了理论研究.计算结果表明:(1)3-氯丙酸在气相中的热消除反应可以通过六元环过渡态机理和四元环过渡态机理平行进行得到产物;(2)2-氯丁酸的热消除则可以通过五元环过渡态机理和四元环过渡态机理平行进行;(3)对3-氯丙酸的热消除反应,以四元环过渡态进行反应的活化势垒较低,而2-氯丁酸的热消除反应则是五元环过渡态机理的反应活化势垒较低.以上两种机理进行反应所得产物产率较高.计算结果与实验一致.

关键词: 3-氯丙酸, 2-氯丁酸, 气相反应, 热消除, 反应机理

Abstract:

3-chloropropionic acid and 2-chlorobutyric acid elimination processes have been studied by semi-empirical MO theory AMI method. The calculated results are consistent with the experimental reports and can be summed up as the following two points: (1) 3-chloropropionic acid gas-phase elimination is a parallel pyrolytic process and occurs via a concerted process with a four-membered cyclic transition state or via a two-step process with a six-membered and a four-membered cyclic transition states. The former is easier to proceed. (2) 2-chlorobutyric acid elimination proceeds in terms of a four-membered cyclic transition state or a five-membered transition state. The former is a concerted process. The five-centred transition state forms an intermediate and eliminate CO further. It is more favored than the four-centered transition state in a dehydrochlorination process.

Key words: 3-chloropropionic acid, 2-chlorobutyric acid, Gas-phase elimination, Reaction mechanism