The solution enthalpy (?Hsoln0) of lidocaine-HCl (LC-HCl) and procaine-HCl (PC-HCl) in water was determined by isoperibolic solution calorimetry at 298.15 K. It was found that ?Hsoln0 for LC-HCl diminishes as the drug concentration increases, whereas the behavior was the opposite for PC-HCl. On the other hand, the calorimetric values obtained as a function of the drug concentration were significantly different with respect to those calculated by using the van t Hoff method, based on solubility determinations at several temperatures. It was demonstrated that the van t Hoff method is not fully reliable for the determination of ?Hsoln0 values in the specific case of highly soluble organic hydrochloride salts. The observed phenomena could be explained by the presence of strong solute-solute interactions at high salt concentrations, in addition to the respective solute-solvent and solvent-solvent interactions.
Compounds
#
Formula
Name
1
C14H23ClN2O
lidocaine hydrochloride
2
C13H21ClN2O2
2-diethylaminoethyl p-aminobenzoate hydrochloride
3
H2O
water
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.