AB-INITIO AND MOLECULAR MECHANICS (MM2 AND MM3) CALCULATIONS OF NONCONJUGATED POSITIVELY CHARGED NITROGEN-CONTAINING COMPOUNDS

High-level ab initio calculations have been performed on N-methyl-N-me thyleneammonium and related compounds to obtain accurate rotational ba rriers, structures, and vibrational frequencies. The 6-31G* basis set has been utilized at the Hartree-Fock level of theory for these calcu lations because little experimental data are available. The MM2(91) an d MM3(94) force fields have been parameterized to include these noncon jugated charged nitrogen-containing compounds. Molecular mechanics geo metries and vibrational frequencies compare well with the ab initio re sults. (C) 1995 by John Wiley & Sons, Inc.