Some novel acyclic Bronsted acidic task-specific ionic liquids (TSILs) that bear an alkane sulfonic acid group in an acyclic trialkanylammonium cation were synthesized and their uses as halogen-free catalysts for regioselective mononitration of aromatic compounds were investigated. The reactions were carried out at 60-80 degrees C with reasonable to good yields and improved para-selectivities for halogenobenzenes compared to those in the absence of the catalysts. In addition, the TSILs could be recovered and reused without noticeably decreasing the catalytic activity. (C) 2008 Elsevier B.V. All rights reserved.