Effect of structural isomerism of propanol or butanol molecules on their enthalpy of dissolution and solvation in water – Methanol mixtures

Abstract

The enthalpies of dissolution of propanol and butanol isomers in mixtures of water with methanol have been measured by the calorimetric method at 298 K and the enthalpies of solvation have been calculated over the entire composition range of mixed solvent. The enthalpy coefficients of methanol–alkanol pair interactions in water and the enthalpy coefficients of water–alkanol interactions in methanol have been computed. The influence of the composition of the mixture, structure and properties of the solutes on the enthalpy characteristics has been considered. The contributions of the structural fragments of alkanol molecules to the enthalpy characteristics of their solutions have been determined within the framework of the previously proposed additive scheme. It is allowed to quantitatively analyze the role of nonspecific and specific solvations of alkanols in solution. It has been shown that the features of solvation of propanol and butanol isomers in a water-methanol mixture are mainly determined by the contribution of specific solvation of hydroxyl groups associated with primary, secondary, and tertiary carbon atoms.