Theoretical Study on the Isomerization Mechanism of Enol Ester from 2-Acyl-1,3-cyclohexanediones

The present paper employed density function theory to investigate two reaction pathways for isomerization of enol ester proposed by Yang(path a) and the present authors(path a), respectively. The base catalytic effects of solvent triethylamine on these two reactions were also evaluated. It is demonstrated that path B is more preferable than path a due to low barrier height for the rate-determining step.

次黄嘌呤氢迁移反应机理的理论研究

采用密度泛函理论方法,在B3LYP/6-31G^(**)水平下研究了无水催化、水催化次黄嘌呤氢迁移反应的微观机理和势能曲线图。计算结果表明:(1)无水催化时次黄嘌呤经过四元环的过渡态,发生分子内氢迁移反应,实现烯醇式向酮式的转变;(2)1分子水催化次黄嘌呤氢迁移反应过渡态的结构为六元环;(3)2分子水催化次黄嘌呤氢迁移反应过渡态的结构为八元环,催化剂存在时发生的是分子间氢迁移反应。能量计算表明,水分子催化下次黄嘌呤氢迁移反应的活化能垒小于无水催化直接H迁移过程的活化能垒,另外,氢键在增大次黄嘌呤水合物稳定性、降低氢迁移反应活化能方面起到非常重要的作用。