Electron exchange and electron transfer of semiquinones in aqueous solutions
Electron exchange and electron transfer of semiquinones in aqueous solutions
复制标题
半醌在水溶液中的电子交换和电子转移
DOI：
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发表时间：
1976
期刊：
影响因子：
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通讯作者：
R. W. Fessenden
中科院分区：
文献类型：
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作者：
D. Meisel;R. W. Fessenden
半醌自由基离子和它们的母体醌之间的自交换电子的速率常数进行了测量，为四个苯醌衍生物在水溶液中（含有5 M 2-丙醇和1 M丙酮在pH 7）。这是通过测量醌的浓度对由原位光解产生的半醌自由基离子的ESR线宽的影响来完成的。研究的醌类有苯醌、2，5-和2，6-二甲基苯醌和杜醌。发现这些对的电子交换速率常数在0.5至2 × 10/sup 8/ M/sup-1/s/sup-1/范围内。用动力学分光光度法和脉冲辐解法测定了这组苯醌衍生物中从一个半醌到另一个醌的电子转移。由于单电子还原电位为所有这些醌/semiquinone夫妇是已知的，从脉冲辐解测定的平衡，电子转移速率可以预测使用马库斯理论的自交换反应的速率。由此得到的计算速率与实验测得的速率常数符合得很好。反应半径可以估计和进一步的电子转移速率和自由能变化之间的相关性进行了检查。
Rate constants for self-exchange of electrons between semiquinone radical ions and their parent quinones were measured for four benzoquinone derivatives in aqueous solutions (containing 5 M 2-propanol and 1 M acetone at pH 7). This was accomplished by measuring the effect of the concentration of the quinone on the ESR line width of the semiquinone radical ion produced by in situ photolysis. The quinones studied were benzoquinone, 2,5- and 2,6-dimethylbenzoquinone, and duroquinone. The rate constants for the electron exchange for these couples were found to be in the range of 0.5 to 2 x 10/sup 8/ M/sup -1/s/sup -1/. Electron transfer from one semiquinone to another quinone in this group of benzoquinone derivatives was measured using kinetic spectrophotometry and pulse radiolysis. Since one-electron reduction potentials for all of these quinone/semiquinone couples are known from pulse radiolysis determination of the equilibria, electron transfer rates can be predicted using the Marcus theory from rates of the self-exchange reactions. The calculated rates thus obtained are in good agreement with the experimentally measured rate constants. Reaction radii could be estimated and further correlations between the rates of electron transfer and the free energy changes were checked.