| Abstract
| - This work deals with exploring some empirical scales of nucleophilicity. We have started evaluating theexperimental indices of nucleophilicity proposed by Legon and Millen on the basis of the measure of theforce constants derived from vibrational frequencies using a probe dipole H−X (X = F,CN). The correlationamong some theoretical parameters with this experimental scale has been evaluated. The theoretical parametershave been chosen as the minimum of the electrostatic potential Vmin, the binding energy (BE) between thenucleophile and the H−X dipole, and the electrostatic potential measured at the position of the hydrogenatom VH when the complex nucleophile and dipole H−X is in the equilibrium geometry. All of them presentgood correlations with the experimental nucleophilicity scale. In addition, the BEs of the nucleophiles withtwo other Lewis acids (one hard, BF3, and the other soft, BH3) have been evaluated. The results suggest thatthe Legon and Millen nucleophilicity scale and the electrostatic potential derived scales can describe in goodapproximation the reactivity order of the nucleophiles only when the interactions with a probe electrophile isof the hard−hard type. For a covalent interaction that is orbital controlled, a new nucleophilicity index usinginformation of the frontier orbitals of both, the nucleophile and the electrophile has been proposed.
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