Kinetic and mechanistic study of the reactions of aryl chloroformates with quinuclidines
作者:Enrique A. Castro、Margarita Aliaga、Paola R. Campodonico、J. Ramón Leis、Luis García-Río、José G. Santos
DOI:10.1002/poc.1116
日期:2006.10
suggests that these mechanisms are stepwise, with the formation of a zwitterionic tetrahedral intermediate (T±) being the rate-determining step. The sensitivity of log kN to the basicity of the nonleaving group (βnlg) is −0.16. By comparing the reactions under investigation between each other and with similar aminolyses, the following conclusions can be drawn: (i) the mechanisms for the quinuclidinolysis
水溶液中(25°C,离子强度0.2 M KCl)在水溶液中(25°C,离子强度0.2 M KCl)监测奎宁核苷与苯基,4-甲氧基苯基,4-氯苯基和4-硝基苯基氯甲酸酯(分别为PClF,MOPClF,ClPClF和NPClF)的反应。进行动力学评估。在胺过量的情况下,发现伪一阶速率系数(k obsd)。的曲线图ķ实测值与[奎宁环]是线性的,与pH非依赖性的斜率(ķ Ñ)。布朗斯台德图(log k N vs. p K a对于PClF,MOPClF,ClPClF和NPClF而言,喹啉鎓离子的线性斜率(β)分别为0.32、0.34、0.31和0.23。斜率的大小表明这些机理是逐步的,两性离子四面体中间体(T ±)的形成是决定速率的步骤。log k N对非离去基团(βnlg)是-0.16。通过比较正在研究的彼此之间的反应和具有相似氨基酸的反应,可以得出以下结论:(i)逐步研究了所研究的四种氯甲酸酯的奎宁环解机理。(ii)以MOPC1F