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首页> 外文期刊>Polyhedron: The International Journal for Inorganic and Organometallic Chemistry >Oxidation of carbohydrates of biological importance by the aquachromium(IV) ion
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Oxidation of carbohydrates of biological importance by the aquachromium(IV) ion

机译：四价铬离子对具有生物重要性的碳水化合物的氧化

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摘要

The oxidation reactions kinetics of a series of related saccharides by aqua-oxo chromium(IV) ion, (H_2O)_5Cr~(IV)O ~(2+), were carried out in perchloric acid aqueous solutions. These reactions yield superoxochromium(III) ion, CrO_2 ~(2+), providing evidence that the two-electron reduction of CrO~(2+) to Cr~(2+) occurred in a single step. In all of these reactions, Cr ~(2+) is the immediate product and could be trapped as CrO _2 ~(2+) when an excess of oxygen was present. The bimolecular rate constants for different aldoses and d-glucitol are independent of [H ~+] in the range 0.1-1.0 M. Relative reactivities of these saccharides toward CrO~(2+) reduction are 1-methyl-α-d-glucopyranose 1-methyl-α-d-galactopyranose ～ 3-O-methyl-d-glucopyranose ～ 6-desoxi-l-galactopyranose ～ 2-desoxi-d-glucopyranose ～ d-glucopyranose d-galactopyranose d-glucitol. The oxidation of aldonic acid such as d-gluconic by CrO2+ showed the same mechanism but the redox process is strongly inhibited when [H~+] increases. Activation parameters were also determined for selected reactions. On the basis of the kinetic result, activation parameters data and oxidized organic products, the mechanism of saccharides oxidation by CrO~(2+) is proposed to be a direct hydride-ion transfer.
机译：在高氯酸水溶液中进行了一系列相关糖类的水合氧化铬（IV）（H_2O）_5Cr〜（IV）O〜（2+）的氧化反应动力学。这些反应产生了超氧铬（III）离子CrO_2〜（2+），这证明了CrO〜（2+）与Cr〜（2+）的两电子还原是一步完成的。在所有这些反应中，Cr〜（2+）是直接产物，当存在过量的氧气时可能被捕获为CrO _2〜（2+）。不同醛糖和d-葡萄糖醇的双分子速率常数在0.1-1.0 M范围内与[H〜+]无关。这些糖对CrO〜（2+）还原的相对反应性是1-甲基-α-d-吡喃葡萄糖 1-甲基-α-d-吡喃半乳糖〜3-O-甲基-d-吡喃葡萄糖〜6-脱氧-1--1-吡喃葡萄糖〜2-脱氧-d-吡喃葡萄糖〜d-吡喃葡萄糖 d-吡喃半乳糖 d-葡萄糖醇。 CrO2 +对d-葡萄糖酸等醛糖酸的氧化机理相同，但当[H〜+]增加时，氧化还原过程受到强烈抑制。还确定了所选反应的活化参数。根据动力学结果，活化参数数据和氧化有机产物，提出糖基被CrO〜（2+）氧化的机理为直接氢离子转移。

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