Electron paramagnetic resonance and electron-nuclear double resonance methods were used to study the polycyclic aromatic radical cations produced in a Friedel-Crafts alkylating sys- tem, with m-xylene, or p-xylene and...Electron paramagnetic resonance and electron-nuclear double resonance methods were used to study the polycyclic aromatic radical cations produced in a Friedel-Crafts alkylating sys- tem, with m-xylene, or p-xylene and alkyl chloride. The results indicate that the observed electron paramagnetic resonance spectra are due to polycyclic aromatic radicals formed from the parent hydrocarbons. It is suggested that benzyl halides produced in the Friedel-Crafts alkylation reactions undergo Scholl self-condensation to give polycyclic aromatic hydrocar- bons, which are converted into corresponding polycyclic aromatic radical cations in the presence of AlCl3. The identification of observed two radicals 2,6-dimethylanthracene and 1,4,5,8-tetramethylanthraeene were supported by density functional theory calculations using the B3LYP/6-31G（d,p）//B3LYP/6-31G（d） approach. The theoretical coupling constants support the experimental assignment of the observed radicals.展开更多
Certain activator was expected to be developed to improve the free radical intermediates relative intensity, and thus to enhance the adhesion between wood fibers when fiberboard was made by laccase treated wood fibers...Certain activator was expected to be developed to improve the free radical intermediates relative intensity, and thus to enhance the adhesion between wood fibers when fiberboard was made by laccase treated wood fibers. Reactive oxygen species (ROS) was detected in laccase-catalyzed oxidation of wood powder using ESR spin trapping technique. The effects of five metal ions (Cu2+, K+, Fe2+, Mg2+, Fe3+) and EDTA on ROS relative strengths were investigated under the condition of pH 5.6 by electron spin resonance spectrometry. The result shows that Cu2+ slightly activates the free radical reaction, and Fe2+ ion has a significant inhibitive effect on the ROS relative strength in the suspension liquid. There is a marked inhibition of the ROS relative intensity when 0.5 mmol/L EDTA is used. The metal ions that enhance laccase activity may be utilized to increase physical properties of fiberboard made by laccase oxidized wood fibers.展开更多
文摘Electron paramagnetic resonance and electron-nuclear double resonance methods were used to study the polycyclic aromatic radical cations produced in a Friedel-Crafts alkylating sys- tem, with m-xylene, or p-xylene and alkyl chloride. The results indicate that the observed electron paramagnetic resonance spectra are due to polycyclic aromatic radicals formed from the parent hydrocarbons. It is suggested that benzyl halides produced in the Friedel-Crafts alkylation reactions undergo Scholl self-condensation to give polycyclic aromatic hydrocar- bons, which are converted into corresponding polycyclic aromatic radical cations in the presence of AlCl3. The identification of observed two radicals 2,6-dimethylanthracene and 1,4,5,8-tetramethylanthraeene were supported by density functional theory calculations using the B3LYP/6-31G（d,p）//B3LYP/6-31G（d） approach. The theoretical coupling constants support the experimental assignment of the observed radicals.
基金This work was supported by the National Natural Science Foundation of China (30471352).
文摘Certain activator was expected to be developed to improve the free radical intermediates relative intensity, and thus to enhance the adhesion between wood fibers when fiberboard was made by laccase treated wood fibers. Reactive oxygen species (ROS) was detected in laccase-catalyzed oxidation of wood powder using ESR spin trapping technique. The effects of five metal ions (Cu2+, K+, Fe2+, Mg2+, Fe3+) and EDTA on ROS relative strengths were investigated under the condition of pH 5.6 by electron spin resonance spectrometry. The result shows that Cu2+ slightly activates the free radical reaction, and Fe2+ ion has a significant inhibitive effect on the ROS relative strength in the suspension liquid. There is a marked inhibition of the ROS relative intensity when 0.5 mmol/L EDTA is used. The metal ions that enhance laccase activity may be utilized to increase physical properties of fiberboard made by laccase oxidized wood fibers.
