Figure 6.

Determination of the EZA protonation enthalpy. (a) ITC raw titration curve of 0.25 mM EZA in water with 1.5 equivalent NaOH titrated with 2.5 mM HNO₃ at 37°C. (b) Integrated ITC curves of EZA (◯) and TFMSA (▲) titration with HNO₃ at 37°C. The first transition represents the neutralization of 0.5 equivalent of NaOH with HNO₃ while the second transition (between the molar ratio of 0.5 and 1.5) represents the titration of the compound. In these experiments the enthalpies of protonation were −21.3 kJ/mol for TFMSA and −27.6 kcal/mol for EZA. (c) The enthalpies of EZA (◯) and TFMSA (▲) protonation as a function of temperature. The slopes yield the heat capacities of protonation equal to 88.7 J/(mol × K) for EZA and 124.7 J/(mol × K) for TFMSA.