Theoretical studies on the reaction mechanism of oxidation of primary alcohols by Zn/Cu(ii)-phenoxyl radical catalyst.
The catalytic mechanism for the oxidation of primary alcohols catalyzed by the two functional models of galactose oxidase (GOase), M(II) L (M = Cu, Zn; L = N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1-2-diiminoquinone)), has been studied by use of the density functional method B3LYP. The catalytic cycle of Cu- and Zn-catalysts consists of two parts, namely, substrate oxidation (primary alcohol oxidation) and O(2) reduction (catalyst regeneration). The catalytic mechanisms have been studied for the two reaction pathways (route 1 and route 2). The calculations indicate that the hydrogen atom transfer within the substrate oxidation part is the rate-determining step for both catalysts, in agreement with the experimental observation. The calculated overall reaction barrier for Cu-catalyst is 16.74 kcal mol(-1), smaller than 22.96 kcal mol(-1) for the Zn-catalyst. This is consistent with the experimental result that the Zn-catalyst is less efficient when compared with the Cu-catalyst. The importance of the solvent effect is demonstrated. Insights into the hydrogen atom transfer process are discussed.
Cheng
Lin
L
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China.
Wang
Jinping
J
Wang
Meiyan
M
Wu
Zhijian
Z
D000438:Alcohols / Q000737:chemistry*; D002384:Catalysis; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry; D005692:Galactose Oxidase / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010636:Phenols / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D000438:Alcohols; D010636:Phenols; C042329:phenoxy radical; D003300:Copper; D006859:Hydrogen; D005692:Galactose Oxidase; D015032:Zinc; D010100:Oxygen