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
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
Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities
作者:Robert J. Mayer、Martin Breugst、Nathalie Hampel、Armin R. Ofial、Herbert Mayr
DOI:10.1021/acs.joc.9b01485
日期:2019.7.19
reactions (C versus O attack) are opposite to the predictions by the principle of hard and soft acids and bases, we performed a comprehensive experimental and computational investigation of phenolate reactivities. Rate and equilibrium constants for the reactions of various phenolate ions with benzhydrylium ions (Aryl2CH+) and structurally related quinone methides have been determined photometrically in polar
is more pronounced indicates that the negative hyperconjugation and π-resonance within the carboxylate moiety is operative in TS. The plots of ΔG‡ vs approximated ΔrG° for solvolysis of benzhydryl aryl/alkyl carbonates and benzhydryl carboxylates reveal that a given carbonate solvolyzes over the higher Marcus intrinsic barrier and over the earlier transition state than carboxylate that produces an anion
通过应用LFER方程log k = s f(E f + N f),可以动力学地研究负超共轭对碳酸二酯溶剂分解行为的影响。碳酸盐二酯的溶剂分解速度比相应的羧酸盐快,并且芳族碳酸盐的增强作用更明显的观察结果表明,羧酸盐部分内的负超共轭和π共振在TS中起作用。Δ的曲线ģ ‡ VS近似Δ - [R ģ用于苯甲酰基芳基/碳酸烷基酯和苯甲酰基羧酸盐的溶剂分解的°表明,与产生类似稳定性阴离子的羧酸盐相比,给定的碳酸盐在较高的马库斯本征势垒和更早的过渡态上进行溶剂化。由于沿反应坐标系发展电子效应的滞后性,与羧酸盐和酚盐的情况相比,固有势垒对碳酸盐的溶剂分解行为的影响更为重要。因此,碳酸盐的溶剂分解反应常数(s f)通常比羧酸盐低。由于碳酸盐的较低的反应常数,芳基/碳酸烷基酯与另一个具有类似核功能性的离去基团(N如果切换基板的电击部分,则可能会发生f)。
A Kinetic Study on Nucleophilic Displacement Reactions of Phenyl Y-Substituted-Phenyl Carbonates with Alkali Metal Ethoxides: Metal Ion Effect and Reaction Mechanism
作者:Ik-Hwan Um、Ji-Yoon Seo、Ji-Sun Kang、Jun-Sung An
DOI:10.1246/bcsj.20120104
日期:2012.9.15
Pseudo-first-order rate constants (kobsd) have been measured for reactions of phenyl Y-substituted-phenyl carbonates with alkalimetal ethoxides (EtOM, M = Li, Na, and K). The plot of kobsd vs. [Et...
已经测量了苯基 Y 取代苯基碳酸酯与碱金属乙醇盐(EtOM,M = Li、Na 和 K)反应的伪一级速率常数 (kobsd)。kobsd vs. [Et...
Kinetics and Mechanism of Nucleophilic Displacement Reactions of Y-Substituted Phenyl Benzoates with Cyanide Ion
作者:Song-I Kim、Eun-Hee Kim、Ik-Hwan Um
DOI:10.5012/bkcs.2010.31.03.689
日期:2010.3.20
Discussion The kinetic study was performed spectrophotometrically. All reactions proceeded with quantitative liberation of Y-substituted phenoxide ion (and/or its conjugate acid) under pseudo-first- order conditions (i.e., the nucleophile concentration in excess over the substrate concentration). The reactions obeyed first- order kinetics and pseudo-first-order rate constants (
Y 取代苯甲酸苯酯 (1) 和苯硫代苯甲酸苯酯 (2) 与 CN 反应的二级速率常数汇总 - 在 80 mol % H 2 O/20 mol % DMSO 中,温度为 25.0 ± 0.1 o C a entry Y p K a 10 2 k CN- / M –1 s –1 12a 4-MeO 10.20 0.843 b 2.13 b 4-Me 10.19 0.783 b 1.89 c 3-CH 3 10.08 0.724 - d H 9.95 1.02 b 2.75 e 4-Cl 9.38 2.32 - f 3-COMe 9.19 3.59 b - g 3-Cl 9.02 4.19 - h 3-CHO 8.98 3.93 - i 4-COOEt 8.50 6.07 - j 3-NO 2 8.35 14.1 b 18.0 k 4-COMe 8.05 7.68 b 7.88 l 4-CN 7