Curved Hammett Plot in Alkaline Hydrolysis of <i>O</i>-Aryl Thionobenzoates: Change in Rate-Determining Step versus Ground-State Stabilization
作者:Ik-Hwan Um、Ji-Youn Lee、Han-Tae Kim、Sun-Kun Bae
DOI:10.1021/jo035854r
日期:2004.4.1
have been measured for alkaline hydrolysis of O-aryl thionobenzoates (X-C6H4-CS-OC6H4-Y) in 80 mol % H2O−20 mol % DMSO at 25.0 ± 0.1 °C. The Hammett plot for the reaction of O-4-nitrophenyl X-substituted thionobenzoates (X-C6H4-CS-OC6H4-NO2, 1a−e) exhibits a downward curvature. However, a possible traditional explanation in terms of a change in the rate-determining step (RDS) has been considered but
已在25.0±0.1°C下在80 mol%H 2 O-20 mol%DMSO中测量了O-芳基硫代苯甲酸酯(XC 6 H 4 -CS-OC 6 H 4 -Y)的碱水解的二级速率常数。哈米特情节为的反应ø -4-硝基苯基X取代thionobenzoates(XC 6 H ^ 4 -CS-OC 6 H ^ 4 -NO 2,1A - ë)呈向下弯曲。但是,已经考虑了关于速率确定步骤(RDS)的更改的可能的传统解释,但被拒绝了。拟议的解释涉及在给定电子的取代基X和硫代羰基官能团之间通过共振相互作用稳定基态(GS),该过程基于针对同一反应获得的线性Yukawa-Tsuno图。用于该反应的布朗斯台德型情节ø -芳基thionobenzoates(C 6 H ^ 5 -CS-OC 6 H ^ 4 -Y,2A -我)是线性的,但表现出许多分散点具有小的β LG(-0.35)。哈米特积为相同的反应显示,而与σ