A semi-empirical self consistent field molecular orbital calculation on pyridine and pyridinium ion including all valence electrons

Abstract

LCAO–SCF–MO calculations are reported for pyridine and the pyridinium ion. The method used is that of Pople and Segal and described by them as CNDO/2. The results are compared with previous treatments on pyridine, particularly the ab initio calculation by Clementi. The dipole moment and ionisation potential of pyridine are calculated and compared with experiment. The ¹H, ¹³C, and ¹⁴N chemical shifts of nuclei in pyridine and the pyridinium ion are computed from the charge densities, and it is shown that neglect of σ polarisation in such calculation is not warranted.