LIFETIMES OF AMINE-WATER AND AMINE-ALCOHOL HYDROGEN-BONDED COMPLEXES IN HYDROXYLIC SOLVENTS - ROLE OF LONDON DISPERSION FORCES IN SOLVATION

The effect of nonpolar groups on the rate constant kH for dissociation of amine-hydrate and amine-alcoholate hydrogen-bonded complexes was studied using N,N-diethyl-m-toluidine (B) as substrate and methanol and 11.47 mole% t-BuOH-88.53 mole% HOH as solvents, kH was obtained by kinetic analysis of rates of proton exchange, measured by the nmr technique, between BH+ and OH protons in the solvent. For B. HOCH3 in methanol, kH = 4.3 X 108 sec-1 at 30°. For B HOH and B HOBu-t in 11.47% t-BuOH-water, kH = 6.6 X 109 and 2.6 X 105 sec-1, respectively, at 25°. The very large effect of alkyl substitution in the hydroxylic molecule on kn can be attributed largely to London dispersion interaction involving the nonpolar groups. © 1969, American Chemical Society. All rights reserved.