Solvent effects on tautomerism equilibria in heterocycles

Abstract

. High-level ab initio quantum mechanical methods have been used to analyze the tautomeric preferences in the gas phase and in aqueous solution of three important five-member heterocycles: 4-(5-)methylimidazole, 5-hydroxyisoxazole, and 3-hydroxypyrazole. Solvent effects have been introduced by means of self-consistent reaction field (SCRF) calculations at the ab initio level using our parametrized version of the polarizable continuum model developed by Miertus, Scrocco and Tomasi (MST), including geometry relaxation upon solvation. The extent to which the MST model, and SCRF methods in general, are suitable for the study of processes of this type is discussed.