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首页> 外文期刊>Chemistry: A European journal >Charge and Delocalisation Effects on the Lipophilicity of Protonable Drugs
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Charge and Delocalisation Effects on the Lipophilicity of Protonable Drugs

机译：电荷和离域对质子化药物亲脂性的影响

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摘要

The transfer mechanisms of ionisable compounds of pharmaceutical interest were studied by cyclic voltammetry at the water/1,2-dichlooethane interface. The partition coefficients of the various ions were deduced from the voltammograms which were monitored as a function of aqueous pH. The dissociation constants and the partition coefficients of the neutral species were determined by a pH-metric titration technique, and the results obtained are displayed in the form of ionic partition diagrams which define the predominace domains of each species in both phases. These diagrams affored an easy interpretation of the mechanisms governing ion transfer and show how neutral species can facilitate the passage of protons from water into an organic phase and thus how ionisable compounds can modulate the pH. The change in lipophilicity between charged and neutral forms of a given compound is discussed in terms of an intramolecular stabilisation of the charge. The nature of the substituents surrounding the charged atom as well as the degree of delocalisation of the charge are shown to contribute markedly to the stabilisation of ionic species in the orgaic phase. Born's solvation model is also used to illustrate qualitatively the effect of themolecular radius on the lipophilicity and to show that ions retainmore wate molecules when they transfer into octanol than into 1,2-dichloroethane.
机译：通过循环伏安法在水/ 1,2-二茂铁乙烷界面上研究了可药用化合物的可离子化化合物的转移机理。从伏安图推导出各种离子的分配系数，该伏安图作为含水pH的函数进行监测。中性物质的解离常数和分配系数通过pH滴定技术确定，所得结果以离子分配图的形式显示，该离子分配图定义了两个相中每种物质的主要结构域。这些图方便地解释了控制离子转移的机理，并显示了中性物质如何促进质子从水进入有机相的通过，从而使可电离的化合物如何调节pH。在给定化合物的带电形式和中性形式之间的亲脂性变化是根据电荷的分子内稳定性来讨论的。已显示带电原子周围的取代基的性质以及电荷的离域程度显着有助于有机相中离子物种的稳定。 Born的溶剂化模型还用于定性地说明分子半径对亲脂性的影响，并显示离子转移到辛醇中比在1,2-二氯乙烷中保留更多的水分子。

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