Ab-initio sto-3G energy of tautomerism for uracil

Abstract

Ab-initio STO-3G energies for uracil (U) and the tautomer 4-hydroxyuracil (U*) are reported. The four highest occupied molecular orbital energies for uracil correlate with experimental photoelectron ionization potentials with a least-squares linear correlation coefficient of 0.999. The energy AE, for U * U* using the best available geometries is 25.5 kcal/mole. The reaction field continuum model for the solvent effect indicates that AE, may be lowered by approximately 3 kcal/mole. Therefore thediketo form of uracil is theoretically determined to be. the most stable form in solution as well as in the gas phase, in complete agreement with experiment.