SEMIEMPIRICAL STUDY OF COMPOUNDS WITH O-H-O INTRAMOLECULAR HYDROGEN-BOND

Application of MNDO, AM1, PM3, MNDO/H, and MNDO/M methods to a set of compounds with intramolecular hydrogen bonds suggested that none of these methods accurately modeled the characteristics of the hydrogen bonds. Since the MNDO/H and MNDO/M methods work well for intermolecular hydrogen bonds, we followed their example and modified MNDO for intramolecular hydrogen bonds by altering the empirical core-core repulsion energy function for all pairs of atoms involved in intramolecular O-H-O bonds. The resulting modified method models the behavior of these bonds quite well, especially as regards their geometry and the barrier to proton transfer.