A MECHANISTIC STUDY OF THE OXIDATION OF PHENOLS IN AQUEOUS-SOLUTION BY OXOIRON(IV) TETRA(N-METHYLPYRIDYL)PORPHYRINS - A MODEL FOR HORSERADISH-PEROXIDASE COMPOUND-II
A MECHANISTIC STUDY OF THE OXIDATION OF PHENOLS IN AQUEOUS-SOLUTION BY OXOIRON(IV) TETRA(N-METHYLPYRIDYL)PORPHYRINS - A MODEL FOR HORSERADISH-PEROXIDASE COMPOUND-II
复制标题
DOI：
10.1039/p29940001139
复制
发表时间：
1994-06-01
期刊：
影响因子：
--
通讯作者：
SMITH, JRL
中科院分区：
文献类型：
--
作者：
COLCLOUGH, N;SMITH, JRL
由四（2-N-甲基吡啶基）卟啉铁（III）和叔丁基过氧化氢生成的氧合铁（IV）四（2-N-甲基吡啶基）卟啉（OFe（IV）T2 MPyP）与3-氰基苯酚在水溶液（pH 7.7）中的反应对苯酚和氧化剂的浓度表现出一级依赖性。在pH 7.7-8.6范围内，苯酚的氧化速率常数与pH值有关，表明苯酚离子是OFe（IV）T2 MPyP氧化的底物.通过苯酚及其6种单取代衍生物的氧化反应，得到了取代基对二级速率常数的影响，并利用Hammett方程和修正的Hammett方程对这些数据进行了分析.结合水溶性受阻酚Trolox C的氧化和[O-H-2（1）]-4-氟苯酚的氧化的EPR研究结果，表明，在这些反应中的速率决定步骤涉及氢原子提取苯酚的氧合铁（IV）的Hammett分析的速率数据从氧化酚类辣根过氧化物酶化合物II已重新审查，并与本研究的那些进行了比较。这导致的结论是，酶促过程涉及的速率决定电子转移从苯酚的氧代血红素。
The reaction of oxoiron(IV) tetra(2-N-methylpyridyl)porphyrin (OFe(IV)T2MPyP), generated from iron(III) tetra(2-N-methylpyridyl)porphyrin and tert-butyl hydroperoxide, with 3-cyanophenol in aqueous solution (pH 7.7) shows first-order dependence on the concentration of the phenol and the oxidant. The pH dependence of the measured second-order rate constant (pH 7.7-8.6) indicates that the phenol, and not the phenolate ion, is the substrate oxidised by OFe(IV)T2MPyP.Substituent effects on the second-order rate constant were obtained from the oxidation of phenol and six monosubstituted derivatives and these data were analysed by Hammett and modified Hammett equations. The rho values obtained, in conjunction with the results from an EPR study of the oxidation of the water soluble hindered phenol, Trolox C, and the oxidation of [O-H-2(1)]-4-fluorophenol, suggest that the rate-determining step in these reactions involves hydrogen atom abstraction from the phenol by the oxoiron(IV) species.The Hammett analyses of rate data from the oxidation of phenols by horseradish peroxidase compound II have been reexamined and compared with those from the present study. This leads to the conclusion that the enzymatic process involves a rate determining electron transfer from the phenol to the oxo-haem.