Reactions of 2,4‐Dinitrophenyl 5‐substituted‐2‐thiophenecarboxylates with R
<sub>2</sub>
NH/R
<sub>2</sub>
NH
<sub>2</sub>
<sup>+</sup>
in 20 Mol % DMSO(aq). Effects of 5‐Thienyl Substituent and Leaving Group on the Reaction Mechanism
作者:Sang Yong Pyun、Kyu Cheol Paik、Man So Han、Bong Rae Cho
DOI:10.1002/bkcs.11857
日期:2019.10
Reactions of 2,4‐dinitrophenyl 2‐thiophenecarboxylate (2a–d) with R2NH/R2NH2+ in 20 mol % DMSO(aq) have been studied. The reactions are overall second order, first order to the substrates, and first order to the nucleophiles. The Brönsted plots showed downward curves with pKa0 = 9.5, β1 = 0.22–0.34, and β2 = 0.85–0.92. The k1 values increased with a stronger electron‐withdrawing 5‐thienyl substituent
研究了2,4-二硝基苯基2-噻吩羧酸酯(2a–d)与R 2 NH / R 2 NH 2 +在20 mol%DMSO(水溶液)中的反应。反应总体上是二级的,对底物的一级,对亲核试剂的一级。该布朗斯台德曲线表明与对向下曲线ķ一个0 = 9.5,β 1 = 0.22-0.34,和β 2 = 0.85-0.92。所述ķ 1值具有更强的吸电子-5-噻吩基取代基和亲核试剂更强增加,而ķ 2 / ķ -1所有5-噻吩基取代基的值几乎相同。5-噻吩基取代基对反应速率的影响在Yukawa-Tsuno图上显示出极好的相关性,其中ρ= 1.28–2.16和r = 0.20–0.60。亲核力越强,ρ值越大,r值越小,这表明羰基碳的电子密度增加,共振需求降低。根据这些结果,提出了一种速率确定步骤有所变化的逐步机制。