Study On Performance And Mechanism Of Electroreduction Aryl Nitro-Compounds

Aryl aminophenol compounds are very important organic chemical materials and intermediates, which are widely applied in pharmacy, pestcide and dye industries. At the present time, preparation of p-aminophenol by electroreduction nitrobenzene is one of the most interesting research fields. In this dissertation, the reduction of nitrobenzenes to the corresponding p-aminophenols was selected out as a model, the effects of the nature and the position of substituted groups on the characteristics of the electroreduction of substituted nitrobenzenes were studied in detail by electrochemical methods such as cyclic voltammery, potentiostatic polarization, chronocoulometry and etc. In addition, the effects of concentration of H2SO4 on the electroreduction behaviors were also investigated .The experimental results showed that the different substituted group on the same location of the benzene cycle, the properties of substituted nitrobenzene were greatly affected by the electronic domino effect and space resistance of the substituted group. An increase in the electron-donor properties of the substituent at different position made the reduction potential more negative and the apparent activity energy more bigger. The current of o-substituted nitrobenzene was affected by both the electronic domino effects and space resistance, while that of m, p-substituted was depend on the electronic domino effects, an increase in the electron-donor properties of substituent made the current more bigger. Due to the effect of the solution, COOH-substituted group had an effect on the electroreduction of nitrobenzene which was different from that of other group.If the same substituted group on the different location of the benzene cycle, the reduction potential of m-substituted nitrobenzene was the most positive and the apparent activity energy was the smallest; While the reduction potential of o-substituted nitrobenzene was the most negative and apparent activity energy was the biggest. The peak current of the p-substituted nitrobenzene was the biggest, and that of o-substituted nitrobenzene was the smallest.The diffusion coefficient was not affected by the nature of the substituted group.