Intrinsic nucleofugality scale within the framework of density functional reactivity theory.

Nucleofugality is a measure of the quality of a leaving group in substitution and elimination reactions. In a conceptual DFT context, the nucleofugality is calculated for an elaborate set of common organic leaving groups, both in the gas phase and in two organic solvents (dichloromethane and methanol). An intrinsic nucleofugality scale is constructed showing fair agreement with the classical trends in leaving group capacity in organic chemistry. The correlation of the results with acidities (tabulated pK(a) values) on one hand and experimental solvolysis reaction rate constants (kinetic parameters) on the other hand is discussed. Finally, a conceptual DFT based formula is derived, describing the influence of the solvation energy on the nucleofugality; excellent correlations were found with explicit calculations for the studied leaving groups.