The Study of Hydrogen Bonding and Related Phenomena by Ultraviolet Light Absorption: Part Iii. The Strength of the Dimeric Hydrogen Bond in Substituted Benzoic Acids as a Measure of Electronic and Steric Interactions

The strength of the intermolecular (dimeric) hydrogen bond in substituted benzoic acids, as estimated from the observed concentration dependence of the ultraviolet absorption spectra, is found to vary with the nature and the position of the substituent. The effects of a number of substituents on the strength of the dimeric hydrogen bond can be rationalized in terms of the usual electronic and steric interactions. The data indicate that o-methoxybenzoic acid forms a stronger intramolecular hydrogen bond than o-fluorobenzoic acid.