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.
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China.
Lin
L
Cheng
Jinping
J
Wang
Meiyan
M
Wang
Zhijian
Z
Wu
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