TRANSFERABILITY OF QUANTUM-MECHANICAL FORCE-FIELD SCALE FACTORS BETWEEN CONJUGATED HYDROCARBONS

The transferability of scale factors (empirical corrections) for quantum mechanical force fields among closely related molecules is tested for the related hydrocarbons, ethylene, 1,3-butadiene, and 1,3,5-hexatriene and their isotopomers. The agreement demonstrated here between the fundamental vibrational frequencies calculated from the scaled quantum mechanical force fields and the experimental frequencies of these molecules confirms this transferability. The advantage of combining quantum mechanical calculations of force constants with empirical scale factors for the accurate prediction of force fields and vibrational frequencies in the analysis of the incomplete experimental spectra of the rotamers of these hydrocarbons is stressed. © 1990.