A Kinetic Study on Nucleophilic Displacement Reactions of Aryl Benzenesulfonates with Potassium Ethoxide: Role of K<sup>+</sup> Ion and Reaction Mechanism Deduced from Analyses of LFERs and Activation Parameters
作者:Ik-Hwan Um、Ji-Sun Kang、Young-Hee Shin、Erwin Buncel
DOI:10.1021/jo302373y
日期:2013.1.18
more reactive than the dissociated EtO–, indicating that K+ ion catalyzes the reaction. The catalytic effect exerted by K+ ion (e.g., the kEtOK/kEtO– ratio) decreases linearly as the substituent X in the benzenesulfonyl moiety changes from an electron-donating group (EDG) to an electron-withdrawing group (EWG), but it is independent of the electronic nature of the substituent Y in the leaving group
Pseudofirst一级速率常数(ķ实测值)已经被分光光度法测量为2,4-二硝基苯基X取代的苯磺酸盐的亲核取代反应4A - ˚F和Y取代的苯基苯磺酸5A - ķ在无水乙醇中与EtOK。的解剖ķ实测值成ķ环氧乙烷-和ķ EtOK(即,二阶速率常数,用于与离解的环氧乙烷的反应中-和离子配对分别EtOK,)示出了离子配对EtOK比离解的环氧乙烷反应性更强–,表示K+离子催化反应。随着苯磺酰基部分中的取代基X从给电子基团(EDG)变为吸电子基团(EWG),K +离子产生的催化作用(例如,k EtOK / k EtO –比)线性降低,但是它与离去基团中取代基Y的电子性质无关。通过线性自由能关系对动力学数据进行分析,得出了通过协调机制进行反应的结论(例如,Brønsted型,Hammett和Yukawa-Tsuno图)。钾+离子通过通过环状过渡态(TS)增加反应中心的亲电子性而不是通过增加离去基团的