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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Localized Electron Transfer in Nonpolar Solution: Reaction of Phenols and Thiophenols with Free Solvent Radical Cations
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Localized Electron Transfer in Nonpolar Solution: Reaction of Phenols and Thiophenols with Free Solvent Radical Cations

机译：非极性溶液中的局部电子转移：苯酚和硫酚与自由基自由基反应

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摘要

Free electron transfer (FET) is understood as the reaction of free and uncorrelated solvent parent radical cations with solutes characterized by a lower ionization potential than those of the solvent. We studied electron transfer from phenols and thiophenols (as solutes) to molecular radical cations of some nonpolar solvents (cyclohexane, n-dodecane, 1,2-dichloroethane, n-butyl chloride) using pulse radiolysis. For phenols (ArOH) as solutes, along with the expected radical cations ArOHo+ , an unexpectedly comparable amount of phenoxyl radicals (ArO") was observed, which evidently arises in a parallel reaction channel of the type shown below with cyclohexane as the solvent: c-C~12+ + ArOH- C-C~12 + ArOHl-+, ArO., H+so1v. Analogous observations were also made for thiophenols as solutes, with ArSHo+ and ArS" simultaneously occurring as reaction products. The appearance of cations and radicals as parallel products can be attributed to two alternative, locally different electron transfer pathways of PET. For example, in the case of phenol it was assumed that transfer starts from either the aromatic ring or the hydroxyl group of the solute. The occurrence of ArO. as a reaction product can then be understood if an efficient transfer barrier prevents rapid charge equilibration in the ionized solute and, therefore, boosts deprotonation. On the basis of quantum chemical calculations, this hypothesis is proven by analyzing the moleclllar oscillations. From the effects observed, general conclusions about PET are derived which characterize this transfer as unhindered, extremely rapid electron jumps from the donors to the holelike solvent radical cations taking place within almost the fIrst collision betVjeen ~e reactants in the solvent cage.
机译：自由电子转移（FET）被理解为自由和不相关的溶剂母体自由基阳离子与溶质的反应，其特征在于电离电位低于溶剂的电离电位。我们使用脉冲辐照研究了电子从苯酚和硫酚（作为溶质）到一些非极性溶剂（环己烷，正十二烷，1,2-二氯乙烷，正丁基氯）的分子阳离子转移。以苯酚（ArOH）为溶质，连同预期的自由基阳离子ArOHo +相比，观察到出乎意料的苯氧基自由基（ArO“）的数量相当可观，显然是在以下所示类型的平行反应通道中，以环己烷为溶剂：cC 〜12 + + ArOH- CC〜12 + ArOH1-，ArO。，H + sov。也观察到类似的观察结果，以硫酚为溶质，同时出现ArSHo +和ArS“作为反应产物。阳离子和自由基作为平行产物的出现可归因于PET的两种替代的，局部不同的电子转移途径。例如，在苯酚的情况下，假定转移从溶质的芳环或羟基开始。发生ArO。如果有效的转移阻挡层阻止了离子化溶质中的快速电荷平衡，从而促进了去质子化，那么可以理解作为反应产物的反应。在量子化学计算的基础上，通过分析分子振荡证明了这一假设。从观察到的效果中，可以得出有关PET的一般结论，该结论将这种转移描述为不受阻碍的，极快的电子从供体跃迁到几乎在溶剂笼中的第一个碰撞反应物中发生的空穴状溶剂自由基阳离子。

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