Some applications of ab initio calculations in molecular spectroscopy

Abstract The utility of ab initio calculations for the determination of structural parameters for allyl halides and ethers is demonstrated. It is shown that calculations with the 6-31G* basis set can be utilized with off-sets for the CH distances of 0.011 A which will give CH distances that agree with the experimental values obtained from infrared frequencies within 0.003 A. When conformers are present, the differences between the structural parameters for the two conformers can be used as constraints for the electron diffraction determination of the structure or for the microwave determinations by utilizing rotational constants from both conformers. Examples are given which show the utility of ab initio calculations for structural determinations, force constants, and frequency predictions.