Structural Identification for the Reaction of Chlorosulfonic Acid with Tertiary N-Donor Ligand – Ionic Liquid or Zwitterionic Compound?

Acid catalysts derived from a well-known reaction of 1-methylimidazole and chlorosulfonic acid system are considered very important, but sufficient details are lacking on their structure information. We studied and report the structural characterization of products from a reaction of 1-methylimidazole and chlorosulfonic acid. Our results from crystallography, nuclear magnetic resonance spectroscopy (NMR), elemental analysis, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) indicate the formation of a unique reaction mixture of zwitterion-type salt [C1im-SO3] and ionic liquid [C1im-SO3H]Cl at a 7:3 ratio instead of only ionic liquids as proposed by others.