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首页> 外文期刊>Journal of the Chemical Society. Perkin Transactions 2 >The oxidation of azo dyes by peroxy acids and tert-butyl hydroperoxide in aqueous solution catalysed by iron(III) 5,10,15,20-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin: product studies and mechanism
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The oxidation of azo dyes by peroxy acids and tert-butyl hydroperoxide in aqueous solution catalysed by iron(III) 5,10,15,20-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin: product studies and mechanism

机译：5,10,15,20-四（2,6-二氯-3-磺酰基苯基）卟啉铁（III）催化过氧酸和叔丁基过氧化氢在水溶液中氧化偶氮染料：产物研究和机理

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Product studies on the oxidation of two 1-arylazo-2-hydroxynaphthalene-6-sulfonate dyes by peroxy acids and by tert-butyl hydroperoxide catalysed by iron(III) 5,10,15,20-tetra(2,6-dichloro-2-sulfonatophenyl)porphyrin in solution have been carried out. In single turnover experiments at pH 11.88, 9.30 and 6.93, dye bleaching by peroxy acids is a two-step process; an initial fast reaction, during which the oxoiron(IV) porphyrin is also formed, is followed by a slow phase involving the regeneration of the iron(III) porphyrin from the oxoiron(IV) porphyrin. The peroxy acid: dye stoichiometry is 1:1 for the initial fast dye bleaching and 2:1 for the slow phase; the latter is equivalent to a 4:1 stoichiometry of oxoiron(IV) porphyrin to dye. In multiple turnover reactions the dye bleaching occurs in two sequential oxidations by oxoiron(IV) porphyrin #pi#-cation radical, each with a peroxy acid: substrate stoichiometry of 1:1. Evidence is presented to show that, in multi-turnover reactions at pH 11.88 where the substrate is the dye anion, the initial product arises from the hydroxylation of the 1-position of the naphthol ring which in the second step is oxidised further to give an azoxy compound. At pH 9.30, where the dyes exist predominantly as the hydrazone tautomers, the initial oxidation generates an azoxy compound which following a Wallach rearrangement is further oxidised on the naphthol ring. More extensive oxidation results in the cleavage of the N-N bond. The iron(III) porphyrin-catalysed dye oxidation with excess of tert-butyl hydroperoxide at pH 6.93, which occurs by hydrogen atom-abstraction, has a hydroperoxide: dye stoichiometry approaching 2:1 and gives the same azoxy product as obtained at pH 11.88 with the peroxyacids. Mechanisms to account for the observed products and stoichiometries are discussed.
机译：铁（III）5,10,15,20-四（2,6-二氯-）催化过氧酸和氢过氧化叔丁基氧化两种1-芳基偶氮-2-羟基萘-6-磺酸盐染料的产物研究已经在溶液中进行了2-磺酰基苯基）卟啉的制备。在pH为11.88、9.30和6.93的单周转实验中，过氧酸对染料的漂白是一个两步过程。在最初的快速反应过程中，还会形成氧代铁（IV）卟啉，随后是一个缓慢的阶段，其中涉及从氧代铁（IV）卟啉再生铁（III）卟啉。最初的快速染料漂白，过氧酸：染料化学计量比为1：1，而对于慢相，染料的化学计量比为2：1。后者相当于氧代铁（IV）卟啉对染料的4：1化学计量。在多次转换反应中，氧漂铁（IV）卟啉＃pi＃阳离子自由基在两个连续的氧化中发生染料漂白，每个自由基的过氧酸：底物化学计量比为1：1。证据表明，在pH为11.88的多次转化反应中，底物是染料阴离子，其初始产物来自萘酚环1-位的羟基化，在第二步中该羟基被进一步氧化，得到一z氧基化合物。在pH 9.30处，染料主要以t互变异构体的形式存在，在初始氧化作用下会生成一种偶氮氧基化合物，在Wallach重排后，该化合物会在萘酚环上进一步氧化。更广泛的氧化导致N-N键的断裂。铁（III）卟啉催化的染料氧化，在过量的pH为6.93的叔丁基氢过氧化物中，通过氢原子的吸收而发生，其氢过氧化物：染料的化学计量比接近2：1，并得到与在pH 11.88中获得的相同的乙氧基产物。与过氧酸。讨论了解释观察到的产物和化学计量的机理。

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