Nitration of aromatic compounds in BrOnsted acidic ionic liquid

Various aromatic compounds, including alkyl and halo benzenes, were nitrated to mononitro compounds in reasonable yields (40%-80%) with NH4NO3 from 0°C to room temperature in Br0nsted acidic ionic liquids with [Hmim] [CF3COO] and [Hmim] [HSO4] as solvent and catalyst respectively. The isomer ratios for nitration of toluene in BrOnsted acidic ionic liquids were comparable to that obtained in mixed acid nitration. Isomer ratios for the nitration of halo benzenes in Br0nsted acidic ionic liquids are different from that obtained in mixed acid nitration, usually, with higher para selectivity. The para-/ortho- product isomer ratio is 6.2 for the nitration of chlorobenzene at 18°. for 8 h with n(TFAA)//n(NH4NO3) = 5. The para-/ortho- product isomer ratio is 14.0 for the nitration of bromobenzene at 0°C for 8 h with n(TFAA)/n(NH4NO3) = 5. The para-product, p-nitrobromobenzene, from the nitration of bromobenzene in [Hmim][HSO4] under 0°C. precipitates with 98% purity, which facilitates the separation of the pure isomer.