The phosphoryl and the carbonyl group as hydrogen bond acceptors

Formation constants for the hydrogen-bonded complexes between phenol (donor) and selected carbonyl or phosphoryl compounds (acceptors) were determined from IR shifts. The P=O group is about two orders of magnitude stronger as an acceptor than the C=O group, but no evidence for the enolization of a -diphosphoryl system was found. The IR absorption band of the phosphoryl group ( P=O ) showed weak response to the involvement in the hydrogen bonding, and the shifts of the donor molecule ( OH ) provide a better measure of the formation constants. Key words: carbonyl and phosphoryl groups as hydrogen bond acceptors, enolization of a -difunctional system, determination of K assoc from the IR shifts.