A MODIFICATION OF THE GENERALIZED BORN THEORY FOR IMPROVED ESTIMATES OF SOLVATION ENERGIES AND PK SHIFTS

We present herein an appraisal on the performance of the generalized B orn (GB) model in estimating the solvation energies of small molecules and pK(a) shifts of dicarboxylic acids. The quality of the solvation energy results obtained with the GB model was exceedingly good as alre ady reported in the literature but the pK(a) shift estimates fell shor t of expectations. Analysis of the problem on a simple prototype syste m revealed that with the GB model, the estimates of the two components , viz. the shielding and the self-energy terms, to be somewhat in erro r. These errors compensate each other in the calculation of solvation energies but affect the intramolecular interaction energies and hence pK shifts differently. We examine here the feasibility of introducing modifications to the GB model for a simultaneous evaluation of both so lvation and intramolecular interaction energies. (C) 1998 American Ins titute of Physics.