We prepared a series of new binary protic ionic liquids (PILs) based on 2-imidazolidone and trifluoroacetic acid and determined their properties such as their viscosity, thermal and electrochemical properties. The results show that these PILs possess a wide liquid state temperature range, relatively good thermal stability, low viscosity and high ionic conductivity. The conductivity of the ionic liquid at a molar ratio of 3:7 was found to be 0.30 S/m and its viscosity was only 7.7 cP at room temperature. With an increase in temperature most of the samples gave better performance. The viscosity and the conductivity of the sample with a molar ratio of 5:5 was 6.1 cP and 0.32 S/m at 60 degrees C, respectively. Infrared spectroscopy showed that the organic molecules coordinate with the H(+) cation and CF(3)COO(-) anion through their polar groups (C=O and NH groups). These properties, therefore, result in these PILs being of interest for application in organic synthesis, especially as catalysts in acid catalytic reactions. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.019111jes] All rights reserved.