coefficient beta gradually decreases from about 0.7 to almost zero. The value of pKa approximately 10 for the intermediate to base-catalysed transformation has been found from this dependence. In the N-methylpyrrolidine and triethylamine buffers, the rate-limiting step of transformation is changed into ring opening of In-, and the general-base-catalysed reaction changes into a specific-base-catalysed one
S- [1-(4-(
甲氧基苯基)
吡咯烷基-2-酮-3-基] -N-甲基-异
硫代
溴化铵转化为2-甲基亚
氨基-5- [2-(4-
甲氧基苯基
氨基)的动力学和反应机理已在25°C和I = 1 mol l-1的条件下在胺缓冲液(pH 8.1-11.5)和
氢氧化钠溶液(0.005-0.5 mol l-1)的
水溶液中研究了乙基]]
噻唑烷-4-酮拟一级反应条件。观察到的动力学表明,转化反应经受普通的碱,普通的酸和氢氧根离子催化。转化的限速步骤是从四面体中间体In分离质子。从动力学数据(pKa = 8.75 +/- 0.10)和电位计确定了S- [1-(4-
甲氧基苯基)-
吡咯烷-2--2-酮-3-基] -N-甲基异
硫脲溴化物的pKa值。滴定(pKa = 8.90 +/- 0。05)。随着酸缓冲液组分的pKa值增加,布朗斯台德系数β的值逐渐从大约0.7降低到几乎为零。从这种依赖性已经发现,对于中间到碱催化的转