EPR法研究对氯四苯基锰卟啉对异丙苯过氧化氢的催化分解作用

EPR Study of Cumene Hydroperoxide Decomposition Catalyzed by Tetra-(p-chlorophenyl)porphinatomanganese Chloride

以5,5-二甲基-1-吡咯啉-N-氧化物(DMPO)为自旋捕捉剂,采用电子顺磁共振波谱(EPR)法研究了对氯四苯基锰卟啉(T(p-Cl)PPMnⅢCl)催化分解异丙苯过氧化氢(CHP)的反应过程.结果表明,在25oC下的初始反应阶段,在T(p-Cl)PPMnⅢCl与CHP的反应体系中仅检测到有异丙苯氧自由基的DMPO自旋加合物.随着CHP浓度的增大,还检测到有异丙苯过氧自由基自旋加合物的重排产物信号.这说明在T(p-Cl)PPMnⅢCl的催化作用下,初始阶段CHP是以O-O键均裂的方式产生异丙苯氧自由基引发分解反应,并主要生成2-苯基-2-丙醇.在较大的初始CHP浓度下,异丙苯氧自由基进一步与CHP反应,产生异丙苯过氧自由基.提出了CHP分解反应的主要自由基历程.

The decomposition of hydroperoxide in the presence of a metalloporphyrin is an important metalloporphyrin-catalyzed hydrocarbon aerobic oxidation reaction.This process affects the oxidation product selectivity,the formation rate of oxidation products,and also the life of the metalloporphyrin catalysts.The decomposition of cumene hydroperoxide（CHP） catalyzed by tetra-（p-chlorophenyl）porphyrinatomanganese chloride（T（p-Cl）PPMnIIICl） was studied by EPR,and 5,5-dimethyl-1-pyrroline N-oxide（DMPO） was used as an EPR spin trap.Experiments revealed that only the cumoxyl radical adduct was present during the initial reaction time at 25 °C.Another kind of radical adduct,a rearrangement product of the cumylperoxyl radical spin adduct,was also detected by EPR when the concentration of CHP was increased.Results further show that CHP decomposition started by homolytic O-O bond cleavage because of the T（p-Cl）PPMnIIICl catalyst generating cumoxyl radicals in the initial part of the reaction and this led to 2-phenyl-2-propanol.The cumylperoxyl radicals were formed from the subsequent reaction of cumoxyl radicals with CHP when the initial CHP concentration increased.A free radical route for this decomposition reaction was also proposed.