【作者】 王永涛； 管俊； 姚加； 李浩然；

【Author】 Yongtao Wang;Jun Guan;Jia Yao;Haoran Li;Department of Chemistry,Zhejiang University;

【机构】 浙江大学化学系；

【摘要】 The mechanism for molecular oxygen oxidation of 2,3,6-trimethylphenol（TMP）or 4-chloro-2,3,6-trimethylphenol（CTP）to 2,3,6-trimethyl-1,4-benzoquinone（TMBQ）catalyzed by CuCl has been studied using DFT calculations,and the effect of added Cl^-was proved to be essential.Dinuclear species（μ-η2:η2-peroxo）dicopper（Ⅱ）has been recommended to be the true catalyst in the oxidation of phenols to benzoquinones^1,2.Thus,we assumed A（Fig.1）to be the catalyst,and by DFT calculations we found a reaction way of the oxidation of TMP or CTP to TMBQ.However,the rate-determining step of TMP to TMBQ was shown to be the abstraction of hydrogen on para-position,and its free energy barrier was very high（21.0 kcal/mol）.This result was in agree with experimental data,which pointed that CuCl could not work until Cl^-was added.Meanwhile,UV-Vis spectrum showed that CuCl^-and Cl^-formed CuCl^2-.Then,we used B（Fig.1）to be the catalyst and found the same rate-determining step,but its free energy barrier was just 17.3 kcal/mol.To our surprise,the added Cl^-made hydrogen abstraction by Cl much easier.However,the rate-determining step was C to D while CTP to TMBQ was concerned,and its energy barrier was low enough that CTP was oxidized easily to TMBQ catalyze only by CuCl.In conclusion,these computational results explained the importance of added Cl^-during the aerobic oxidation of TMP to TMBQ catalyzed by CuCl.更多还原

【Abstract】 The mechanism for molecular oxygen oxidation of 2,3,6-trimethylphenol（TMP） or 4-chloro-2,3,6-trimethylphenol（CTP） to 2,3,6-trimethyl-l,4-benzoquinone（TMBQ） catalyzed by CuCl has been studied using DFT calculations,and the effect of added Cl^- was proved to be essential.Dinuclear species（μ-η2:η2-peroxo）dicopper（Ⅱ） has been recommended to be the true catalyst in the oxidation of phenols to benzoquinones^1,2.Thus,we assumed A（Fig.1）to be the catalyst,and by DFT calculations we found a reaction way of the oxidation of TMP or CTP to TMBQ.However,the rate-determining step of TMP to TMBQ was shown to be the abstraction of hydrogen on para-position,and its free energy barrier was very high（21.0 kcal/mol）.This result was in agree with experimental data,which pointed that CuCl could not work until Cl^- was added.Meanwhile,UV-Vis spectrum showed that CuCl and Cl^- formed CuCl^2-.Then,we used B（Fig.1） to be the catalyst and found the same rate-determining step,but its free energy barrier was just 17.3 kcal/mol.To our surprise,the added Cl^- made hydrogen abstraction by Cl^- much easier.However,the rate-determining step was C to D while CTP to TMBQ was concerned,and its energy barrier was low enough that CTP was oxidized easily to TMBQ catalyze only by CuCl.In conclusion,these computational results explained the importance of added Cl^- during the aerobic oxidation of TMP to TMBQ catalyzed by CuCl.更多还原