The substituent effects in the Birch reduction reaction of substituted benzenes are discussed. Anonplanar, boat-form conformation is suggested for the benzene radical anion formed by the transfer of an electron to a s...The substituent effects in the Birch reduction reaction of substituted benzenes are discussed. Anonplanar, boat-form conformation is suggested for the benzene radical anion formed by the transfer of an electron to a substituted benzene molecule. In this conformation ,the 1,4-dienyl radical anion has two double bonds isolated, the negative charge is localized on posion 6 and the single electron is on position 3, the farthest position from the negative chareg, when the substituent is electron-withdrawing. Both alkyl and alkoxy groups are considered to be electron-withdrawing. These substituents should be activating groups for their inductive effect. The reaction rate decreasing of alkyl benzenes may be cansed by reasons other than electronic effect. The reduction of benzoic acid and benzamide, in which 1,4-dihydro benzenes are obtained, is considered to be an exceptional example, in which an extra stabilized Y-aromatic radical anion may be invilved.展开更多
Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synth...Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.展开更多
Substituent effect of metal porphyrin molecular catalysts plays a crucial role in determining the catalytic activity of oxygen electrocatalysis.Herein,substituent position effect of Co porphyrins on oxygen electrocata...Substituent effect of metal porphyrin molecular catalysts plays a crucial role in determining the catalytic activity of oxygen electrocatalysis.Herein,substituent position effect of Co porphyrins on oxygen electrocatalysis,including the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER),was investigated.Two Co porphyrins,namely 2,4,6-OMe-CoP and 3,4,5-OMe-CoP,were selected as the research objects.The ORR and OER performance was evaluated by drop-coating molecular catalysts on carbon nanotubes(CNTs).The resulted 3,4,5-OMe-CoP/CNT exhibited high bifunctional electrocatalytic activities and better long-term stability for both ORR and OER than 2,4,6-OMe-CoP/CNT.Furthermore,when applied in the Zn-air battery,3,4,5-OMe-CoP/CNT exhibited comparable performance to that with precious metal-based materials.The enhanced catalytic activity may be attributed to the improved charge transfer rate,mass transfer and hydrophilicity.This work provides an effective strategy to further enhance catalytic activity by introducing substituent position effect,which is of great importance for developing more efficient energy-related electrocatalysts.展开更多
文摘The substituent effects in the Birch reduction reaction of substituted benzenes are discussed. Anonplanar, boat-form conformation is suggested for the benzene radical anion formed by the transfer of an electron to a substituted benzene molecule. In this conformation ,the 1,4-dienyl radical anion has two double bonds isolated, the negative charge is localized on posion 6 and the single electron is on position 3, the farthest position from the negative chareg, when the substituent is electron-withdrawing. Both alkyl and alkoxy groups are considered to be electron-withdrawing. These substituents should be activating groups for their inductive effect. The reaction rate decreasing of alkyl benzenes may be cansed by reasons other than electronic effect. The reduction of benzoic acid and benzamide, in which 1,4-dihydro benzenes are obtained, is considered to be an exceptional example, in which an extra stabilized Y-aromatic radical anion may be invilved.
文摘Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.
基金support from the National Natural Science Foundation of China(Nos.21808138 and 21773146)Fok Ying-Tong Education Foundation for Outstanding Young Teachers in University,Fundamental Research Funds for the Central Universities(Nos.GK202103029 and GK202103045)+2 种基金Young Talent fund of University Association for Science and Technology in Shaanxi,ChinaChina Postdoctoral Science Foundation(No.2019T120877)Research Funds of Shaanxi Normal University。
文摘Substituent effect of metal porphyrin molecular catalysts plays a crucial role in determining the catalytic activity of oxygen electrocatalysis.Herein,substituent position effect of Co porphyrins on oxygen electrocatalysis,including the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER),was investigated.Two Co porphyrins,namely 2,4,6-OMe-CoP and 3,4,5-OMe-CoP,were selected as the research objects.The ORR and OER performance was evaluated by drop-coating molecular catalysts on carbon nanotubes(CNTs).The resulted 3,4,5-OMe-CoP/CNT exhibited high bifunctional electrocatalytic activities and better long-term stability for both ORR and OER than 2,4,6-OMe-CoP/CNT.Furthermore,when applied in the Zn-air battery,3,4,5-OMe-CoP/CNT exhibited comparable performance to that with precious metal-based materials.The enhanced catalytic activity may be attributed to the improved charge transfer rate,mass transfer and hydrophilicity.This work provides an effective strategy to further enhance catalytic activity by introducing substituent position effect,which is of great importance for developing more efficient energy-related electrocatalysts.
