Heat Capacity and Thermodynamic Properties of Sulfonate-Containing Zwitterions

Two sulfonate-containing zwitterions, 1-methylimidazolium-3-propylsulfonate zwitterion (MimC(3)SO(3), C7H12N2O3S; CAS 179863-07-1) and 1-methylimidazolium-3-butylsulfonate zwitterion (MimC(4)SO(3); C8N14O3S; CAS 148019-49-2), were prepared, and the structures were characterized by H-1 NMR and C-13 NMR and ESI-MS. The thermodynamic properties are investigated through adiabatic caloremetry (AC). differential scanning calorimetry (DSC). and thermogravimetric (TG) analysis. The low-temperature heat capacity (C-p,C-m) of MimC(3)SO(3) and MimC(4)SO(3) was measured in the temperature range from (78 to 400) K with a high precision automated calorimeter. The thermodynamic functions [H-T - H-298.15] and [S-T - S-298.15] were calculated based on the heal capacity data in the range from (80 to 400) K with an interval of 5 K.