SOLVATION ENTHALPIES OF VARIOUS NONELECTROLYTES IN WATER PROPYLENE CARBONATE AND DIMETHYL SULFOXIDE

The heats of solution of a number of nonelectrolytes, mostly alcohols and hydrocarbons, have been measured in the solvents water, propylene carbonate, and dimethyl sulfoxide at solute concentrations low enough so that solute-solute interactions are negligible. The solvation energies for the aliphatic compounds exhibit additive group contributions in propylene carbonate and dimethyl sulfoxide and a nonadditive structural" contribution in water. This simple analysis is less successful for the aromatic compounds. The structural effect in the enthalpy of hydration of the normal alcohols ranges from about -2.5 kcal/mol for methanol to about -8.5 kcal/mol for amyl alcohol. Its plot as a function of chain length tends to level off near amyl alcohol. The enthalpy of the hydrogen bond from a normal alcohol to the solvent is near -8.1 kcal/mol in dimethyl sulfoxide and -6.2 kcal/mol in propylene carbonate."