SOLVATION OF SOME AMIDES IN MIXED-SOLVENT SYSTEMS - COMPARISON OF THE RESULTS OF INFRARED SPECTROSCOPIC AND CALORIMETRIC MEASUREMENTS

Spectroscopic studies of the -C = O stretching vibration of amides in a series of mixed solvents, containing at least one hydroxylic component, allow the determination of the relative populations of di-, mono- and non-hydrogen bonded species. These results have been analysed in terms of a simple equilibrium model and the results of this treatment are compared with the results of the analyses of the enthalpies of transfer. These analyses provide detailed information about the extent of preferential solvation of the different amide functions groups in mixed solvent systems. They also point to marked differences in the sensitivity of polar and non-polar surfaces of these solutes to changes in the structure of the methanol-water system.