Quantum similarity approach to LFER: substituent and solvent effects on the acidities of carboxylic acids

Quantum similarity measures were used to estimate dissociation constants fo r acid-base equilibria. It is proposed that the dissociation constant of a carboxylic acid may be described by the electronic density function of the COOH group and quantified by the self-similarity measure of this fragment. In addition, using a polarized continuum model, the inclusion of surroundin g medium effects on the electronic density function of the solute is easily taken into account, and in this way the solvent effect on acid dissociatio n constants can be simply described. A successful correlation was obtained between dissociation constants of a variety of acids in different solvents and quantum selfsimilarity measures of the COOH fragment. Copyright (C) 199 9 John Wiley & Sons, Ltd.