Oxidation of ascorbate anion by electron transfer to phenoxyl radicals.
Oxidation of ascorbate anion by electron transfer to phenoxyl radicals.
复制标题
通过电子转移至苯氧基自由基来氧化抗坏血酸阴离子。
DOI：
10.2307/3574655
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发表时间：
1977
影响因子：
3.4
通讯作者：
R. H. Schuler
中科院分区：
文献类型：
--
作者：
R. H. Schuler
大多数苯氧基自由基通过简单的电子转移过程迅速使用氧化物抗坏血酸阴离子（速率为4至20 x 10/sup 8/m/sup -1/sec/sup -1/）。在360 nm处的特征性折磨，其延伸系数为3300 m/sup -1/cm/sup -1/，在OH对苯酚攻击产生的苯氧基自由基的情况下，氧化似乎是抗焦酸盐仅被氧化较小的自由基，例如酒精自由基，para-丝氨基酮或苯基自由基抗坏血酸自由基阴离子仅在390 nm以上弱吸收，苯氧基和葡萄糖酮自由基更强烈地吸收抗坏血酸，可用于检查检查的氧化。在苯氧基和半氨基酮自由基的情况下，通过对para-氟苯酚的氟位置的攻击来说明了这种应用。 E/sub aq // sup-的溴苯酚与以前的光学研究相一致。通过在正骨和para-Isomers的情况下，羟基苯基自由基阴离子的快速质子化，但在元异构体的情况下却没有。«较少
Most phenoxyl radicals rapidly oxidize ascorbate anion (rate constants from 4 to 20 x 10/sup 8/ M/sup -1/ sec/sup -1/) by a simple electron transfer process. The product radical anion is relatively unreactive and has a well-characterized absorption at 360 nm where it has an extinction coefficient of 3300 M/sup -1/ cm/sup -1/. In the case of a phenoxyl radical produced by OH attack on phenol, oxidation appears to be quantitative. Ascorbate is oxidized only slowly or not at all by less reactive radicals, such as the alcohol radicals, para-semiquinones, or the phenyl radical. Ascorbate can, therefore, be used to selectively remove phenoxyl radicals from many mixed radical systems. Because ascorbate radical anion absorbs only weakly above 390 nm, where phenoxyl and para-semiquinone radicals absorb more strongly, ascorbate can be used to examine the oxidation of substrates in cases where phenoxyl and semiquinone radicals are produced simultaneously. This application is illustrated by a study of the attack of OH at the fluorine position of para-fluorophenol. A second illustrative example is provided by a study of the tertiary oxidation of ascorbate following reduction of the bromophenols by e/sub aq//sup -/. It is shown, in agreement with previous optical and ESR studies,more » that phenoxyl radicals are produced by rapid protonation of the hydroxyphenyl radical anion in the case of the ortho- and para-isomers but not in the case of the meta-isomer.« less