Characterisation of the water/o-nitrophenyl octyl ether system in terms of the partition of nonelectrolytes and of ions

The Abraham linear free energy relationship, or solvation equation, has been applied to literature data on the partition of nonelectrolytes in the water to o-nitrophenyl octyl ether (NPOE) system. The resulting equation is compared to equations for other water to solvent systems using the D-parameter of Abraham and Martins and the theta-parameter of Ishihama and Asakawa. It is shown that as a solvent in partitioning systems, NPOE quite resembles nitrobenzene and 1,2-dichloroethane, and that the latter does not resemble an alkane-like solvent. Using descriptors for simple ions that we have previously obtained, we show that ions and nonelectrolytes can be included in the same linear free energy relationship.