The complete harmonic force fields and the in-plane and out-of-plane vibrational fundamentals of 4H-pyran-4-one are determined by CNDO/2 and MINDO/3 semiempirical quantum chemical methods. The quadratic force constants are scaled using 11 scale factors. In the case of MINDO/3 a standard set of scale factors is used, while in the case of CNDO/2 they are refined. The latter, optimized set of scale factors, is very similar to those published for other molecules. The theoretical vibrational spectra calculated from these scaled quantum mechanical (SQM) force fields are in fair agreement with the experimental gas-phase spectra, confirming the applicability of semiempirical force field calculations for vibrational spectra analysis. The choice of the reference geometry is shown to have only a small effect on the scale factors. Dependence of the scale factors on related geometry parameters is predictable, although other factors (e.g., anharmonic vibrations versus harmonic theoretical treatment) also make important contributions to the final values of the scale factors.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry