INVESTIGATION OF RELATIONSHIPS BETWEEN SOLUTE MOLECULE SURFACE ELECTROSTATIC POTENTIALS AND SOLUBILITIES IN SUPERCRITICAL FLUIDS

We have sought to relate the electrostatic potentials of naphthalene and some indole derivatives, computed at the ab initio Hartree-Fock STO-5G//STO-3G level, to their experimentally determined solubilities in four supercritical fluids (C2H6, C2H4, CO2, and CHF3). Very good correlations were found between solubility and the sum of the variances of the positive and negative potentials on the solute molecular surfaces; these relationships are quantitatively similar for all four solvents. For oxindole, we conclude that the enol tautomer predominates in these solutions. The inclusion of solute molecule surface areas and volumes did not improve our correlations.