碱金属氯化物催化下甲醛与丙二腈Knoevenagel缩合反应的理论研究

采用量子力学计算中的密度泛函DFT方法,在B3LYP/6-311++G(d,p)水平上,研究了LiCl、NaCl及KCl催化条件下甲醛与丙二腈Knoevenagel缩合反应的机理。计算结果表明:动力学方面甲醛与丙二腈的缩合反应分两步进行,反应的第一步为整个反应的速度控制步骤;从热力学方面看,整个反应为放热反应。催化剂LiCl、NaCl、KCl对反应的第一步影响较大,促进了此步亲核反应的进行及活泼氢的迁移,使反应更容易进行。催化剂的加入降低了反应的势垒,且催化效果是LiCl好于NaCl,NaCl好于KCl。

Theoretical Studies on the Knoevenagel Condensation Reaction of Formaldehyde with Methylene Dicyanide Catalyzed by Alkali Metal Chlorides

The Knoevenagel condensation reactions of formaldehyde with methylene dicyanide uncatalyzed and catalyzed by LiCl, NaCl and KCl had been studied using DFT method at B3LYP/6 -311 ＋ ＋ G（d, p） level. The kinetics analysis demonstrated that the condensed reaction of formaldehyde with methylene dicyanide was through two steps and the first step was the rate - controlled step; The thermodynamics analysis indicated demonstrated that the reaction was exothermie. The results showed that nucleophilic reaction and H - shift in the first step were assisted by catalysts of LiCl, NaCI and KCl, and the reactions were easier. The catalysts reduced the potential barrier of the reaction. The potential barriers of reactions with catalysts were lower than that of no catalyst. According to the theoretical results, LiCl was more favorable than that of NaCl and NaCl was more favorable than that of KCl.