Kinetics of the Reaction of β-Methoxy-α-nitrostilbene with Cyanamide in 50 DMSO−50 Water. Failure to Detect the S<sub>N</sub>V Intermediate
作者:Claude F. Bernasconi、Aquiles E. Leyes、Zvi Rappoport
DOI:10.1021/jo990044u
日期:1999.4.1
anion (CNA(-), pK(a) = 11.38) rather than the neutral amine that is the reactive species. Attempts at monitoring the reaction with the neutral CNA at low pH were unsuccessful because of competing hydrolysis. It is shown that the nucleophilic reactivity of CNA is abnormally low, probably because of a resonance effect, and that the reactivity of CNA(-) is high, higher than that of strongly basic oxyanion
在8.5至12.4的pH范围内,β-甲氧基-α-硝基苯乙烯(1-OMe)与氰胺(CNA)反应的动力学研究表明它是阴离子(CNA(-),pK(a)= 11.38 )而不是反应性物种中性胺。由于竞争性水解,未能在低pH下监测与中性CNA反应的尝试未成功。结果表明,CNA的亲核反应性异常低,这可能是由于共振效应所致;而CNA(-)的反应性较高,是由于溶剂化程度较弱,高于强碱性氧阴离子。1-OMe和CNA(-)的高反应性似乎构成了有利于检测S(N)V中间体的有利条件,就像1-OMe与硫醇盐离子,醇盐离子,和一些胺。然而,没有观察到中间体。讨论了此失败的原因。