Kinetics and Mechanism of the Nucleophilic Displacement Reactions of Chloroacetanilide Herbicides: Investigation of α-Substituent Effects
作者:Katrice A. Lippa、Sandra Demel、Irvin H. Lau、A. Lynn Roberts
DOI:10.1021/jf030290d
日期:2004.5.1
ease with which alpha-chloroacetanilide herbicides undergo displacement reactions with strong nucleophiles, and their recalcitrance toward weak ones, is intimately related to their herbicidal properties and environmental chemistry. In this study, we investigate the kinetics and mechanisms of nucleophilic substitution reactions of propachlor and alachlor in aqueous solution. The role played by the alpha-amide
α-氯代乙酰苯胺除草剂与强亲核体发生取代反应的难易程度以及对弱亲核体的拒服性与它们的除草特性和环境化学密切相关。在这项研究中,我们研究了水溶液中丙草胺和甲草胺的亲核取代反应的动力学和机理。通过包括具有修饰的α取代基的几种丙草胺的结构上相关的类似物,检查了α-酰胺基团所起的作用。反应的整体二级性质,负DeltaS(双匕首)值,离子强度对反应性的弱影响,结构反应性趋势共同支持分子间的S(N)2机理,而不是丙氯的α-氯代乙酰苯胺以及α-氯代硫代乙酰苯胺类似物的分子内反应。相反,α-亚甲基类似物表现出动力学和盐效应,与苯胺氮的邻氨基苯甲酸酯辅助相一致。可以推断出与α-苯胺取代基的电子相互作用,而不是与邻近基团的参与,可以控制α-氯乙酰苯胺对亲核试剂的反应性。