COMPARISON OF THEORETICAL-MODELS OF SOLVATION

In this work, we examine several continuum models for estimating the f ree energy of solvation. We find statistically that the best overall o ne-parameter fit depends only on whether there is a hydrogen bond or n ot. Within the non-hydrogen-bonded set of molecules, a three-parameter fit including molecular volume, molecular surface area, and the elect rostatic component from any reaction field model is quite successful. We do not find a strong bias for any of the dielectric models, althoug h the PCM model of Tomasi and co-workers seems to slightly surpass the others. Within the hydrogen-bonded set of compounds, a good fit can b e obtained simply by considering the surface accessible area of each a tom, together with a dispersion and electrostatic interaction descript or (a six-parameter fit). Such a model, containing primarily nonquantu m chemical descriptors, extrapolates very well to the solvation energi es of the non-hydrogen-bonded set with an overall R(2) = 0.9334. (C) 1 996 John Wiley & Sons, Inc.