second‐order polynomial equation. This kinetic behavior is in agreement with a stepwise mechanism consisting of two tetrahedral intermediates, one zwitterionic (T±) and the other anionic (T−), with a kinetically significant proton transfer from T± to an aniline to yield T−. The rate equation was derived from the proposed mechanism. By nonlinear least‐squares fitting of the rate equation to the experimental data
的反应Ô(4-甲基苯基) - š - (4-
硝基苯基)二
硫代
碳酸酯和Ô(4-
氯苯基) - š - (4-
硝基苯基)二
硫代
碳酸酯与一系列
苯胺经受在44重量%的
乙醇动力学调查-
水,温度25.0°C,离子强度为0.2M。分光光度法在420 nm(
4-硝基苯硫醇根阴离子的外观)上跟踪反应。在过量胺下,发现伪一阶速率系数(k obs)。对于两种底物与
苯胺的反应,k obs 对根据二阶多项式方程,恒定pH下的游离胺浓度呈非线性向上变化。此动力学行为是在具有由两个四面体中间体,一种两性离子(T的逐步机构协议±)与其它阴离子(T - )中,用从T A动力学显著质子转移±为
苯胺,得到Ť - 。速率方程是从提出的机制中得出的。通过速率方程与实验数据的非线性最小二乘拟合,确定了两个步骤中涉及的速率微系数的值。版权所有©2009 John Wiley&Sons,Ltd.