2,4-二氯苯氧乙酸代谢中的水解反应机理  

Hydrolysis Reaction Mechanism of 2,4-Dichlorophenoxy Acetic Acid Metabolism

作　　者：李佳[1] 徐雯丽[1] 胡静[1] 凌敏[1] 姚建华[1] 

机构地区：[1]中国科学院上海有机化学研究所,上海200032

出　　处：《物理化学学报》2013年第9期1923-1930,共8页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金项目(21072216);国家科技部"十二五"支撑项目(2011BAE06B05);国家重点基础研究发展规划项目(973)(2010CB126103)资助~~

摘　　要：2,4-二氯苯氧乙酸(2,4-D)是应用广泛的农用除草剂和植物生长素,在它的代谢过程中,涉及多种化学反应.本文采用密度泛函理论B3LYP方法,分别研究了它在代谢过程中的三条水解反应途径的机理.研究结果表明:(Ⅰ)2,4-D水解反应有两种模式,C(1)―O键解离的氢转移和C―Cl键解离的氯被取代.(II)C―Cl键的解离能垒明显低于C(1)―O键的解离能垒,即水解速率较快,反应动力学占优势.在三条反应途径中,途径(2)和(3)优先水解C―Cl键,再水解C(1)―O键.由于受反应速率的影响,不同中间体在降解过程中的浓度有明显区别.(Ⅲ)对于水解反应,采用导体极化连续模型(CPCM)考虑溶剂化效应,可更合理地阐述水解反应机理.Abstract： 2,4-Dichlorophenoxy acetic acid （2,4-D） is a herbicide and plant growth regulator that is widely applied in agriculture. Many chemical reactions take place in the metabolism of 2,4-D. Herein, the hydrolysis reaction mechanism in 2,4-D metabolism will be presented. In this study, a density functional theory approach, B3LYP, was employed to investigate the hydrolysis reaction mechanism along three different paths. The computed results indicate that： （I） there are two models of the hydrolysis reaction of 2,4-D. The dissociation mechanism of C（1 ）-- O and C--CI involve hydrogen transfer and CI substitution, respectively. （11） The energy barrier of C--CI dissociation was lower and the dissociation showed advantageous dynamics. Two of the reaction paths that initiate the dissociation of C--CI were primary reactions. The dissociation of C（1）--O was the last step in the primary reactions and had a higher energy barrier. In metabolism, the different intermediates have different concentrations, and this impacts on the reaction rate. （111） In addition, it was necessary to consider the solvent effect to investigate the hydrolysis reaction. To characterize the solvent effect, the conductor-like polarizable continuum model （CPCM） was used to simulate the hydrolysis reaction with respect to the bond length and energy barrier.

关 键 词：2 4-二氯苯氧乙酸 密度泛函理论 反应机理 势能面 水解 溶剂化效应 

分 类 号：O643.12[理学—物理化学]