In this work, the acid cleavage at 25 degrees C in 20% v/v aqueous ethanol of a series of analogues of piperidine dithiocarbamate X(C2H4)2NCS2(-) (X = CH2, CHCH3, NH, NCH3, S, O) was studied. The pH-rate profiles were obtained in the range of H(o)-5 and pH 5. They all presented a dumbell shaped curve with a plateau from which the pH-independent first-order rate constant k(o) (or the specific acid catalysis
在这项工作中,在25%的20%v / v
乙醇水溶液中的
哌啶二
硫代
氨基甲酸酯X(
C2H4)2
NCS2(-)(X =
CH2,CHCH3,NH,NCH3,S,O)类似物的酸裂解被研究了。在H(o)-5和pH 5的范围内获得了pH速率分布图。它们都呈现出一个哑铃形曲线,并具有一个平稳平台,从该平台可以得出与pH无关的一阶速率常数k(o)(或特定的除了DTC的游离(pKa)和共轭酸(pK(+))种类的酸解离常数外,还计算了酸催化k(H))。动力学确定的pKa和pK(+)对pKN(母体胺的pKa)的LFER用于表征反应速率物种和速率确定步骤过渡态的结构。对于X = ,CH3CH的k(H)值与logDk(H)对pKN的布朗斯德图的强碱区域中的alkDTC值一致,其中过渡态接近分子内
水催化S-N形成的两性离子二
硫代
氨基甲酸的质子转移。但是,当X = NH,CH 3N,O,S时,反应性物质是DTC阴