Density functional study of three-protonated hypoxanthine3+ isomeric forms

The chemical and physicochemical properties of purine derivatives and isomers have received special attention for several years, The Density Functional Theory study of three-protonated hypoxanthine(3+) is presented here. Total molecular energies, relative energetic stabilities, several molecular and electronic structure properties, Delta(G) over bar values of the heterocyclic protonic transfer processes, the isomeric equilibrium constant and the IR vibrational spectra for the two possible enolic isomeric forms of tricationic hypoxanthine were calculated. The theoretical properties are discussed and compared with those homologues for the most stable tautomers showing lower protonation levels. The resulting theoretical trends for several properties are then employed successfully to analyze some features of the experimental physicochemical and chemical behavior of hypoxanthine, thus leading to postulate some factors associated with the remarkable instability of hypoxantine(3+). (C) 2000 Elsevier Science B.V. All rights reserved.