A new method of solvation analysis: applications to quinones.

A new method of analysis of the factor contributing to solvation of small molecules is described. Approximations of the energetic contributions to the entry of a molecule into water have been derived from partition coefficient data of solutes and selected derivatives from a multiplicity of solvents. These include taking separate account energy of the cost of introduction of a molecular cavity in water, the strength of solute-water dipolar interactions, and the strengths of hydrogen bond formation with water of the lone pairs and hydroxylic hydrogens associated with the molecule. In this report the solvation-free energies of benzoquinone and hydroquinone in water are described. We also consider the solvation of the semiquinone anion and show it to be fundamentally different from that of either the quinone or hydroquinone; this is discussed as a potentiality for selective binding ("solvation") of quinone, semiquinone and hydroquinone in sites of redox catalysis such as those found in the photosynthetic reaction center.