Force field in the hydroxylamine molecule from ab intio MO calculation

Abstract

Sixty-nine anharmonic force constants of hydroxylamine were calculated by an ab initio Hartree-Fock SCF MO method with the 4-31G* basis set. The calculated fundamental frequencies which include the anharmonic effects are still larger than the observed frequencies by = 6%. This is because of the overestimation of the quadratic force constants rather than inaccurate anharmonic constants. The characteristics of geometries and force constants are compared for three amines, methylamine. hydrazine, and hydroxylamine, and they are interpreted by a model of the orbital interactions of the fragment radicals which constitute each molecule.