Characteristic infrared absorption frequencies of organophosphorus compounds—I The phosphoryl (PO) group

The frequency limits, between which the phosphoryl valence vibration is found, are tabulated for over 900 organophosphorus compounds distributed between 69 general types of structure. These correlations are further broken down to cover more detailed structures, in those cases for which the evidence shows the frequency to vary significantly with changes in the structure. The dependence of the phosphoryl frequency upon the inductive effects of substituent groups attached to the phosphorus atom is also discussed. A modified linear relationship between the phosphoryl frequency and the sum of the ‘phosphorus inductive (II) constants’ is proposed together with new and revised values for such constants. The accuracy of the relationship is shown to be better than ± 12 cm−1 for most of the compounds considered. The partial failure of the relationship for some classes of organophosphorus compounds is discussed in terms of possible perturbing factors such as hydrogen bonding, resonance, tautomerism and field effects.