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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mechanism and Kinetics of Photoisomerization of a Cyclic Disulfide, trans-4,5-Dihydroxy-1,2-dithiacyclohexane
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Mechanism and Kinetics of Photoisomerization of a Cyclic Disulfide, trans-4,5-Dihydroxy-1,2-dithiacyclohexane

机译：环二硫，反式-4,5-二羟基-1,2-二硫代环己烷的光致异构化机理和动力学

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摘要

The photolysis of trans-4,5-dihydroxy-1,2-dithiacyclohexane in aqueous and CH_2Cl_2 solution yields two isomers of 2,3-dihydroxy-1-mercaptotetrahydrothiophene, characterized by ~1H and ~(13)C NMR and negative ion electrospray mass spectrometry. Product formation in water is independent of the presence of oxygen and the concentration of trans-4,5-dihydroxy-1,2-dithia-cyclohexane and involves intramolecular 1,5-H-transfer, followed by cyclization through thiophilic or nucleophilic addition, or 1,2-H-transfer, followed by cyclization through the recombination of a sulfur- and a carbon-centered radical. In contrast, the quantum yields for reaction in CH_2Cl_2 solutions are dependent on both oxygen concentration and on the concentration of trans-4,5-dihydroxy-1,2-dithiacyclohexane. The latter results are consistent with an intermolecular H-transfer between an initial dithiyl diradical and trans-4,5-dihydroxy-1,2-dithia-cyclohexane. Time-resolved laser flash photolysis studies indicate rapid product formation on the submicrosecond time scale and support the intermediacy of -mercaptoalkyl radicals.
机译：反式-4,5-二羟基-1,2-二硫代环己烷在水溶液和CH_2Cl_2中的光解产生2,3-二羟基-1-巯基四氢噻吩的两种异构体，其特征在于〜1H和〜（13）C NMR及负离子电喷雾质谱。水中的产物形成与氧气的存在和反式-4,5-二羟基-1,2-二硫代-环己烷的浓度无关，并且涉及分子内的1,5-H转移，然后通过亲硫或亲核加成进行环化，或1,2-H-转移，然后通过以硫和碳为中心的基团的重组而环化。相反，在CH_2Cl_2溶液中反应的量子产率既取决于氧浓度，也取决于反式4,5-二羟基-1,2-二硫代环己烷的浓度。后者的结果与初始二硫代双自由基和反式-4，5-二羟基-1，2-二硫代-环己烷之间的分子间H-转移相一致。时间分辨的激光闪光光解研究表明，在亚微秒级范围内迅速形成产物，并支持-巯基烷基自由基的中介作用。

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