Hardness and bond index profiles of hydrogen-bonded complexes with single-minimum and double-minimum potentials

Abstract The dissociation reaction, H 3 N · HF → H 3 N + HF and the proton-transfer reaction (F-H · Cl) − → (F· H-Cl) − have been studied at the HF//6-31G ∗∗ level in order to understand the progress of these reactions in terms of global and local reactivity parameters. Both the reactions are found to obey the maximum hardness principle. The potential energy curve for the proton transfer reaction passes through a transition state wherein the hardness is at a minimum. In this reaction bond index profiles of the bonds being broken and formed intersect at the point corresponding to the maximum in the potential energy curve. Condensed Fukui functions have been calculated at different stages of dissociation of H 3 N · HF. Variation of reactivity of a particular site towards electrophilic, nucleophilic or radical attack is properly reflected in these values.