Hydrogen bonding in diols and binary diol-water systems investigated using DFT methods. II. Calculated infrared OH-stretch frequencies, force constants, and NMR chemical shifts correlate with hydrogen bond geometry and electron density topology. A reevaluation of geometrical criteria for hydrogen bonding.
Although the two hydroxyl groups in 1,2-diols interact as evidenced by NMR and IR spectroscopic shifts, electron density topological analysis has shown a bond critical point (BCP) and atomic bond path to be absent (Klein, R. A.; J Comp Chem 2002, 23, 585-599; J Am Chem Soc 2002, 124, 13931-13937), indicating that no intramolecular hydrogen bond is formed. Here, we demonstrate that small NMR or IR shifts are neither necessarily diagnostic nor sufficient as indicators of hydrogen bond formation; moreover, modified van der Waals atomic radii are needed for estimating maximum nuclear interaction distances and nuclear interpenetration.
Klein
Roger A
RA
Institute for Physiological Chemistry, University of Bonn, Nussallee 11, D-53115 Bonn, Federal Republic of Germany. klein@institut.physiochem.uni-bonn.de