The equilibrium geometry of pyridazine have been determined by ab initio Hartree-Fock gradient method with 4-21 basis set. This theoretical equilibrium geometry has been corrected to approximate the gas phase r(s) structure assuming that the errors in ab initio Hartee-Fock method are systematic. Most of the corrected geometry parameters are in very good agreement with those of an earlier microwave study. The remaining parameters - the C3-N2 and C3-C4 bond lengths - determined experimentally only by electron diffraction method, show as much as -0.015 and +0.010 Å difference from the experimental ones respectively. The complete harmonic force field has also been determined at 4-21 Hartree-Fock level. The harmonic force constants have been scaled by using scale factors previously derived by fitting the computed force field of benzene to the observed benzene vibrational spectrum. The scaled quantum mechanical force field obtained this way reproduces the fundamental vibrational frequencies of pyridazine-h4 and pyridazine-d4 within the accuracy of 15 cm-1 in most cases, which gives a good basis for re-examining the spectral assignment made in previous experimental studies .
|Number of pages||1|
|Publication status||Published - Jan 1 1990|
ASJC Scopus subject areas
- Pharmaceutical Science