Study On Regioselective Nitration Of Aromatic Compounds On Solid Acid Catalysts

Clean synthesis of nitro aromatic compounds is an important trend in the development of nitration. A series of solid acid catalysts, including Ti02-Pillared clay, S042-/ZrO2, S042-/TiO2,SO42-/TiO2-ZrO2, SO42-/WO3-ZrO2 and SO42-/Mo03-ZrO2 etc., have been prepared and characterized. Regioselectivities of chlorobenzene nitration on these catalysts were investigated. It was found that the para-selectivity of chlorobenzene nitration was enhanced and the yields of mononitro compounds of halobenzene were over 98.0% when using nitric acid as nitrating agent. The ortho-para-isomer ratios, in product distribution of chlorobenzene mononitration, were varied in range from 0.36 to 1.11 on solid acid catalysts by using NO2 as nitrating agent. The electron spin densities of radical cations of chlorobenzene were calculated by an UAM1 method, and it was found that the electron spin density distribution of chlorobenzene radical cations were changed by transition-metal cations. Regioselectivities of nitration of chlorobenzene on solid acid catalysts were elucidated in terms of one-electron transfer nitration mechanism.