PARTIAL MOLAR VOLUMES OF ALKYLATED URACILS - INSIGHT INTO THE SOLVATION SHELL - PART-II

The solute-solvent interactions in aqueous solutions of alkylated urac ils are discussed. The partial molar volume data are interpreted using a new model of interaction of the solute molecule with the solvent. T he model is based on the assumption that the density of solvent in the hydration shell depends on the structure and polarity of the solute m olecule. The relation among molecular volume, partial molar volume, an d volume of the solvation shell is expressed by alpha parameter, alpha which is defined as the relative density of the solvation shell. It i s found that in compounds with the same number of CH2- groups, the alp ha values depend on substitution on the C or N atoms of the uracil ske leton. The alpha values also depend to some extent, on screening of th e oxygen atoms by methylation of the neighboring atoms of the uracil r ing. A correlation is presented between the relative density of solvat ion shell and polarity (defined as the ratio of the surface of polar g roups and atoms exposed to the solvent to the total accessible molecul ar surface of the molecule) for the compounds studied. It was demonstr ated that of the various solute-solvent interactions the dominant role is played by polar interactions.