Kinetics and Mechanism of the Reactions of Anilines with Ethyl <i>S</i>-Aryl Thiocarbonates
作者:Enrique A. Castro、Leonardo Leandro、Pablo Millán、José G. Santos
DOI:10.1021/jo982063u
日期:1999.3.1
pK(a) of anilinium ions) are linear, with slopes beta = 0.9 for DNPTC, in agreement with a stepwise mechanism where the breakdown of a tetrahedral addition intermediate (T(+/-)) is rate determining, and beta = 0.54 for TNPTC, consistent with a concerted mechanism. Consideration of the results for aminolysis from the present work and those from previous studies leads to the following conclusions. (i) The
苯胺与S-(2,4-二硝基苯基)硫代碳酸乙酯(DNPTC)和S-(2,4,6-三硝基苯基)硫代碳酸乙酯(TNPTC)的反应在水溶液中于25.0℃下进行动力学研究。离子强度0.2(KCl)。通过分光光度法(400 nm)释放相应的取代苯硫醇根阴离子来研究反应。在苯胺过量的情况下,找到伪一阶速率系数(k(obsd))。k(obsd)与[N](N为游离取代的苯胺)的关系呈线性且与pH无关,斜率为k(N)。Brönsted型图(苯胺离子的log k(N)vs pK(a))是线性的,DNPTC的斜率β= 0.9,这与逐步机理有关,其中四面体加成中间体(T(+ / -))是速率确定的,对于TNPTC,β= 0.54,与协调机制一致。考虑目前工作和以前研究得出的氨解结果,得出以下结论。(i)具有2,4-二硝基苯硫基的四面体中间体比包括2,4,6-三硝基苯硫基的中间体更稳定。(ii)具有2,4,6-三硝基