Molecular Geometry as a Source of chemical Information. Part I: How H-Bonding Modifies Molecular Structure in the Vicinity of Hydrogen Donating Group. The Case of Phenol Derivatives Interacting with Nitrogen and Oxygen Bases

Analysis of geometrical patterns of 635 variously substituted phenols in H-bonding complexes with bases revealed that C1O, C1C2, C1C6 bond lengths as well as ipso bond angle change regularly with variation of the acidity (pKa) of phenols. The Bent-Walsh rule is fulfilled and the approximate linear dependence between the above mentioned geometry parameters works. The perturbation in the OH group, due to H-bonding, is transmitted even on further fragments of the ring. DFT modelling at the B3LYP/6-311+G** level of theory for the simplest cases illustrate nicely the conclusion derived for variously substituted systems.