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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Identification of Radicals and Determination of Their Yields in the Radiolytic Oxidation of Glycine. Time-resolved ESR Methodology
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Identification of Radicals and Determination of Their Yields in the Radiolytic Oxidation of Glycine. Time-resolved ESR Methodology

机译：甘氨酸的辐射氧化中自由基的鉴定及其产率的确定。时间分辨的ESR方法论

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摘要

Both aminomethyl (~.CH_2NH_2) and H_2N-~.CH-CO_2~- radicals were identified by time-resolved ESR spectroscopy in the oxidation of glycine anions by ~.OH. Previous ESR measurements had detected only the H_2N-~.CH-CO_2~- radical in these systems. The rise times of the ESR lines for these two different radicals are consistent with both of the radicals being formed in the initial reaction of ~.OH with the glycine anions. The yields of these two C-centered radicals relative to the total yield of ~.OH are approximately 29% for aminomethyl radicals and 53% for H_2N-~.CH-CO_2~- radicals. The yield of aminomethyl radicals from methylamine was 53%. No ESR lines attributable to aminyl radicals could be directly detected in solutions of glycine (HN~.-CH_2-CO_2~-) at high pH or low pH, or in solutions of methylamine (HN~.-CH_3). However, clear evidence for the presence of the aminyl radicals was obtained in spin-trapping experiments using the aci-anion form of nitromethane with both methylamine and glycine. The rapid appearance of aminomethyl radicals in a complementary experiment with hydrated electrons reacting with N-chloroglycine could be simply explained on the basis of the formation of N-centered radicals in this situation. The ESR method for determining the yields was tested in the ~.Oh oxidation of methylamine and succinic acid. The implications of the findings of this work are discussed in the context of the recently proposed scheme for the oxidation of glycine anions by ~.OH.
机译：在〜.OH氧化甘氨酸阴离子时，通过时间分辨ESR光谱法鉴定了氨基甲基（〜.CH_2NH_2）和H_2N-〜.CH-CO_2〜-自由基。先前的ESR测量在这些系统中仅检测到H_2N-〜.CH-CO_2〜-自由基。这两个不同基团的ESR线的上升时间与〜.OH与甘氨酸阴离子的初始反应中形成的两个基团一致。相对于〜.OH的总产率，这两个以C为中心的自由基的产率对于氨基甲基自由基而言约为29％，对于H_2N-〜.CH-CO_2-自由基而言约为53％。来自甲胺的氨基甲基自由基的产率为53％。在高pH或低pH的甘氨酸（HN〜.-CH_2-CO_2〜-）溶液或甲胺（HN〜.-CH_3）溶液中都没有直接检测到可归因于氨基自由基的ESR谱线。然而，使用硝基甲烷的乙酰阴离子形式与甲胺和甘氨酸同时进行的自旋捕集实验获得了存在氨基自由基的明确证据。在这种情况下，以N为中心的自由基的形成可以简单地解释在与水合电子与N-氯甘氨酸反应的互补实验中氨基甲基自由基的快速出现。用于确定收率的ESR方法是在甲胺和琥珀酸的〜.h氧化中测试的。在最近提出的用〜.OH氧化甘氨酸阴离子的方案的背景下讨论了这项工作的发现的意义。

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