Reaction of nitroxides with 1,5-dihydroflavins and N3,5-dimethyl-1,5-dihydrolumiflavin.
Reaction of nitroxides with 1,5-dihydroflavins and N3,5-dimethyl-1,5-dihydrolumiflavin.
复制标题
硝基氧与 1,5-二氢黄素和 N3,5-二甲基-1,5-二氢亮黄素的反应。
DOI：
10.1021/ja00464a031
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发表时间：
1977
影响因子：
15
通讯作者：
T. C. Bruice
中科院分区：
文献类型：
--
作者：
T. Chan;T. C. Bruice
Kinetic studies of the le-transfer from 1, 5-dihydroflavins (FIH2= IIH2 to VIIIH2) and 3, 5-dimethyl-1, 5-dihydrolumiflavin (FIHCH3) to the nitroxides IX, X, and XI are reported. Under the pseudo-first-order conditions of [nitroxide= X]>[FIHCH3], the oxidation to FIHCH3 proceeds in two one-electron transfer steps yielding 3, 5-dimethyllumiflavin (F10x+ CH3) with the intermediacyof the flavin radical species F1CH3-(Xmax 585, 505 nm). In the process, two X are converted to thecorresponding hydroxylamine. The rate of formation of FICH3·(0.78 M-1 s-1) exceeds that of its disappearance (3 X 10-2 M-1 s-1) by 26-fold at pH 8.9. When employing a number of nitroxides with FIHCH3, the logarithm of the second-order rate constants for the formation of FICH3· is found to be a linear function (slope 6.0) of the£ 1/2 of nitroxide. The reaction of the nitroxide XI with 1, 5-dihydroisoalloxazines (IIH2 to VIIIH2) at pH 9 was found to be first order in appearance of oxidized flavin (Flox) when nitroxide was in excess. Below pH 9 and in the absence of a great excess of nitroxide, the spectral time course of the reaction suggests the accumulation of F1H-as its disproportionation dimer [ie,(F1H2-F10X)]. The slope of the plot of log A2 vs. nitroxide£ 1/2 for le-transfer from 1, 5-dihydroflavin (VIIIH2) to nitroxides is found to be the same as found for le “
