Kinetics of Oxidation of 2,6-Dimethylphenol (DMP) Using Novel μ-Carbonato [(Pip)_4nCu₄X₄(CO₃)₂] Complexes  

作　　者：Mohamed A. El-Sayed Hoda A. Elwakeil Ahmed H. Abdel Salam Hemmat A. Elbadawy Mohamed A. El-Sayed;Hoda A. Elwakeil;Ahmed H. Abdel Salam;Hemmat A. Elbadawy(Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt;Chemistry Department, Faculty of Science, University of Jeddah, Jeddah, KSA)

机构地区：[1]Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt [2]Chemistry Department, Faculty of Science, University of Jeddah, Jeddah, KSA

出　　处：《Open Journal of Inorganic Chemistry》2016年第3期183-194,共13页无机化学期刊（英文）

摘　　要：This paper reports the kinetics of the oxidation of 2,6-dimethylphenol (DMP) to get 3,3’,5,5’-tetra- methyl-4,4’-diphenoquinone (DPQ) using novel oxidative coupling complexes [(Pip)_4nCu₄X₄-(CO₃)₂] (n = 1 or 2, X = Cl or Br, Pip = piperidine). The new prepared tetranuclear complexes were characterized using cryoscopic measurements, electronic spectra, FTIR, EPR and cyclic voltammetry techniques. These complexes are catalytically active. The proposed mechanism of the catalytic oxidative coupling can be illustrated as a pre-equilibrium, K, between the catalyst and DMP to form a complex intermediate which is converted to activated complex through the rate determining step, k₂, to form the final product. The inverse of the observed rate constants k_obsd versus 1/[DMP]² gives a straight line with intercept. From the slope and the intercept, both K and k₂ are obtained. At different temperatures, thermodynamic and kinetic parameters are evaluated. It is worth to mention that, the dependence of k_obsd on [DMP]² indicates that the coordination number for every copper center in both n = 1 or 2 in [(Pip)_4nCu₄X4(CO₃)₂] is equal to six. Therefore, carbonato bridging centers in n = 1 acts as a tridentate ligand, while for n = 2 acts as a bidentate ligand.This paper reports the kinetics of the oxidation of 2,6-dimethylphenol (DMP) to get 3,3’,5,5’-tetra- methyl-4,4’-diphenoquinone (DPQ) using novel oxidative coupling complexes [(Pip)_4nCu₄X₄-(CO₃)₂] (n = 1 or 2, X = Cl or Br, Pip = piperidine). The new prepared tetranuclear complexes were characterized using cryoscopic measurements, electronic spectra, FTIR, EPR and cyclic voltammetry techniques. These complexes are catalytically active. The proposed mechanism of the catalytic oxidative coupling can be illustrated as a pre-equilibrium, K, between the catalyst and DMP to form a complex intermediate which is converted to activated complex through the rate determining step, k₂, to form the final product. The inverse of the observed rate constants k_obsd versus 1/[DMP]² gives a straight line with intercept. From the slope and the intercept, both K and k₂ are obtained. At different temperatures, thermodynamic and kinetic parameters are evaluated. It is worth to mention that, the dependence of k_obsd on [DMP]² indicates that the coordination number for every copper center in both n = 1 or 2 in [(Pip)_4nCu₄X4(CO₃)₂] is equal to six. Therefore, carbonato bridging centers in n = 1 acts as a tridentate ligand, while for n = 2 acts as a bidentate ligand.

关 键 词：Catalysts Kinetics THERMODYNAMIC Copper Complexes 

分 类 号：O62[理学—有机化学]