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首页> 外文期刊>Chemistry: A European journal >Quantification of Ion-Pairing Effects on the Nucleophilic Reactivities of Benzoyl- and Phenyl-Substituted Carbanions in Dimethylsulfoxide
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Quantification of Ion-Pairing Effects on the Nucleophilic Reactivities of Benzoyl- and Phenyl-Substituted Carbanions in Dimethylsulfoxide

机译：定量对二甲基亚砜中苯甲酰基和苯基取代的碳的亲核反应性的离子配对效应的定量分析

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摘要

Second-order rate constants for the reactions of acceptor-substituted phenacyl (PhCO-CH--Acc) and benzyl anions (Ph-CH--Acc) with diarylcarbenium ions and quinone methides (reference electrophiles) have been determined in dimethylsulfoxide (DMSO) solution at 20 degrees C. By studying the kinetics in the presence of variable concentrations of potassium, sodium and lithium salts (up to 10(-2) mol L-1), the influence of ion-pairing on the reaction rates was examined. As the concentration of K+ did not have any influence on the rate constants at carbanion concentrations in the range of 10(-4)-10(-3) mol L-1, the acquired rate constants could be assigned to the reactivities of free carbanions. The counter ion effects increase, however, in the series K+ < Na+ < Li+, and the sensitivity of the carbanion reactivities toward variation of the counter ion strongly depends on the structure of the carbanions. The reactivity parameters N and s(N) of the free carbanions were derived from the linear plots of log k(2) against the electrophilicity parameters E of the reference electrophiles, according to the linear-free energy relationship log k(2)(20 degrees C)= s(N)(N+E). These reactivity parameters can be used to predict absolute rate constants for the reactions of these carbanions with other electrophiles of known E parameters.
机译：已在二甲亚砜（DMSO）中确定了受体取代的苯甲酰基（PhCO-CH-Acc）和苄基阴离子（Ph-CH-Acc）与二芳基碳鎓离子和醌甲基化物（参比亲电试剂）反应的二级速率常数溶液在20摄氏度下进行。通过研究在可变浓度的钾盐，钠盐和锂盐（最高达10（-2）mol L-1）存在下的动力学，研究了离子对对反应速率的影响。由于K +的浓度对10（-4）-10（-3）mol L-1范围内的碳负离子的速率常数没有任何影响，因此可以将获得的速率常数分配给游离碳负离子的反应性。但是，抗衡离子效应在K +

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