作者:Enrique A. Castro、Magdalena Acuña、Claudia Soto、Carolina Trujillo、Bárbara Vásquez、José G. Santos
DOI:10.1002/poc.1399
日期:2008.9
The reactions of 4-methylphenyl and 4-chlorophenyl 4-nitrophenyl carbonates (1 and 2, respectively), phenyl, 4-methylphenyl, 4-chlorophenyl, and 4-nitrophenyl 2,4-dinitrophenyl carbonates (3, 4, 5, and 6, respectively), and bis(2,4-dinitrophenyl) carbonate (7) with a series of pyridines are studied kinetically at 25.0 °C in 44 wt% ethanol–water and an ionic strength of 0.2 M (KCl). The reactions are
的4-甲基苯基和4-氯苯基4-硝基苯基碳酸酯(反应1和2,分别地),苯基,4-甲基苯基,4-氯苯基,和4-硝基苯基2,4-二硝基苯基碳酸酯(3,4,5,和分别在图6中显示)和带有一系列吡啶的碳酸双(2,4-二硝基苯酯)(7)在25.0°C下在44 wt%的乙醇-水中和0.2 M(KCl)的离子强度下进行动力学研究。用分光光度法跟踪反应,并在过量胺下发现拟一级反应系数(k obs)。对于所有这些反应,k obs的图在恒定pH值下,游离胺浓度与游离胺浓度呈线性关系,斜率(k N)与pH值无关。布朗斯台德型图(吡啶的共轭酸的log k N对p K a)都是双相的(在高和低p K a处为线性部分,并且在其之间存在曲率)。这些图符合两性离子四面体中间体(T ±)的逐步机理,并且随着吡啶碱度的降低,速率确定步骤从T ±形成到分解到产物的过程均发生了变化。还研究了底物的离去基团,非离去基团和亲电基团以及