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首页> 外文期刊>Chemistry: A European journal >Mechanism of the catalytic deperoxidation of tert-butylhydroperoxide with cobalt(II) acetylacetonate
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Mechanism of the catalytic deperoxidation of tert-butylhydroperoxide with cobalt(II) acetylacetonate

机译：叔丁基氢过氧化物与乙酰丙酮钴（II）催化脱氧的机理

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The Co~(II)/Co~(III)-induced decomposition of hydroperoxides is an important reaction in many industrial processes and is referred to as deperoxidation. In the first step of the so-called Haber-Weiss cycle, alkoxyl radicals and Co~(III)-OH species are generated upon the reaction of the Co~(II) ion with ROOH. The catalytic cycle is closed upon the regeneration of the Co~(II) ion through the reaction of the Co~(III)-OH species with a second ROOH molecule, thus producing one equivalent of the peroxyl radicals. Herein, the deperoxidation of tert-butylhydroperoxide by dissolved cobalt(II) acetylacetonate is studied by using UV/Vis spectroscopy in situ with a noninteracting solvent, namely, cyclohexane. Kinetic information extracted from experiments, together with quantum-chemical calculations, led to new mechanistic hypotheses. Even under anaerobic conditions, the Haber-Weiss cycle initiates a radical-chain destruction of ROOH propagated by both alkoxyl and peroxyl radicals. This chain mechanism rationalizes the high deperoxidation rates, which are directly proportional to the cobalt concentration up to approximately 75 μM at 333 K. However, at higher cobalt concentrations, a remarkable decrease of the rate is observed. The hypothesis put forward herein is that this remarkable autoinhibition effect could be explained by the hitherto overlooked chain termination of two Co~(III)-OH species. The direct competition between the first-order Haber-Weiss initiation and the second-order termination can indeed explain this peculiar kinetic behavior of this homogeneous deperoxidation system. Autoinhibition: Co~(II) ions initiate a radical-chain deperoxidation of tert-butylhydroperoxide propagated by peroxyl and alkoxyl radicals (see picture). The Co~(II) ion is thereby converted into a Co~(III)-OH species, which can either induce initiation upon reaction with ROOH or termination upon the mutual association reaction of two Co ~(III)-OH species. This behavior results in maximum deperoxidation activity as a function of the total cobalt concentration.
机译：Co（II）/ Co（III）诱导的氢过氧化物的分解是许多工业过程中的重要反应，被称为脱氧。在所谓的Haber-Weiss循环的第一步中，Co-（II）离子与ROOH反应生成烷氧基和Co-（III）-OH。通过Co-（III）-OH物种与第二个ROOH分子的反应，在Co-（II）离子再生后，催化循环结束，从而产生一当量的过氧自由基。在此，通过使用非相互作用溶剂即环己烷原位使用UV / Vis光谱法研究了溶解的乙酰丙酮钴（II）对氢过氧化叔丁基的过氧化。从实验中提取的动力学信息以及量子化学计算产生了新的机理假说。即使在厌氧条件下，Haber-Weiss循环也会引发烷氧基和过氧基自由基传播的ROOH的自由基链破坏。这种链机制使高的过氧化率合理化，这与在333 K时高达约75μM的钴浓度成正比。但是，在较高的钴浓度下，观察到速率明显降低。本文提出的假设是，这种显着的自抑制作用可以用迄今被忽视的两个Co〜（III）-OH的链终止来解释。一阶Haber-Weiss引发和二阶终止之间的直接竞争确实可以解释这种均相过氧化系统的特殊动力学行为。自抑制作用：Co〜（II）离子引发由过氧自由基和烷氧基自由基传播的叔丁基氢过氧化物的自由基链脱氧（见图）。 Co-（II）离子从而被转化为Co-（III）-OH物质，其可以在与ROOH反应时诱导引发，或者在两种Co-（III）-OH物质的相互缔合反应时终止。该行为导致最大的过氧化活性为总钴浓度的函数。

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