The contributions of mass and force-constant effects to the carbonyl-stretching frequency of acetyl, carbonyl and benzoyl halides

Abstract

The value of the carbonyl-stretching frequency in molecules of the type COXY is determined not only by the CO force constant, but also by the masses of X and Y, the molecular configuration, and the remaining force constants. A numerical analysis of the dependence of ν co on these factors allows us to estimate a correction to the observed carbonyl frequency which takes into account these extraneous effects and leads to a frequency ν co ∗ which truly reflects the strength of the CO bond. In the acetyl, carbonyl and benzoyl halides the value of ν co ∗ has been found to be almost independent of the nature of the halogen substituent.