1-Ethyl (butyl)-3-methylimidazolium methanesulfonaties: Low-temperature heat capacity and standard thermodynamic functions of formation

A comprehensive study of the thermodynamic properties of two ionic liquids 1-ethyl-3-methylimidazolium (EmimMS) and 1-butyl-3-methylimidazolium methanesulfonate (BmimMS) was carried out. The isobaric heat capacity of the crystal and liquid phases of EmimMS and BmimMS was determined in the temperature range from 80 to 380 K by vacuum adiabatic calorimetry. The heat capacities of EmimMS and BmimMS were assessed at temperatures from 5 to 80 K by the Kelly method. The temperature dependencies of EmimMS and BmimMS main thermodynamic functions were determined in the temperature range from 5 to 380 K (isobaric heat capacity C_p,m(T), standard entropy S^o_m(T), heat content H^o_m(T) – H^o_m(0), Gibbs energy content G^o_m(T) – H^o_m(0). Melting points and fusion enthalpies of EmimMS and BmimMS have been refined by DSC. The enthalpies of dissolution in water of EmimMS and BmimMS at 298.15 K were measured by the dissolution calorimetry. The standard enthalpies, entropies and Gibbs energies of EmimMS and BmimMS formation in the crystal and liquid state at 298.15 K were calculated from the experimental data. Comparison of the obtained thermodynamic characteristics with the literature data was carried out.