STATIONARY POINT STRUCTURE AND ENERGETICS - DENSITY-FUNCTIONAL STUDY INCLUDING SOLVENT EFFECTS ON THE TAUTOMERIZATION OF FORMAMIDE AND 2-PYRIDONE

Solvent effects on the thermodynamics and kinetics of some tautomerization reactions, chosen as the most representative of this wide class of reactions, are analyzed. Solvent effects have been modeled by the self-consistent reaction field approach that we have implemented in the ADF package. We investigated the structure and energetics of the saddle points for the formamide/formamidinic acid and 2-pyridone/2-hydroxypyridine tautomerizations. Our results, carried out both at local and gradient corrected levels, are in good agreement with previous post-Hartree-Fock computations in predicting the structure and the energy of the investigated saddle points. On the other hand, our computations show that solvent effects play a relevant role on the energetics of the reactions. In particular, the interconversion of 2-hydroxypyridine into 2-pyridone is sensibly favored in aqueous solution, being that the latter tautomers are stabilized by solvent interactions. This latter result is in agreement with experimental findings. (C) 1995 John Wiley & Sons, Inc.