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For a number of functional groups, the group electronegativity and hardness in the gas phase and in different solvents was calculated using the recently introduced self-consistent isodensity polarized continuum model (SCI-PCM). The results indicate that the groups become less electronegative and less hard with increasing dielectric constant. Using the calculated functional group properties and Sanderson's electronegativity equalization principle, charge distributions in the alkyl alcohols X−OH and their conjugated bases XO- (with X = −CH3, −CH2CH3, and −CH(CH3)2 are determined in solution. The calculated charge distributions are used in a study of the inversion of alkyl alcohol acidity from gas phase to aqueous solution. Relative acidities are calculated in the gas phase and in aqueous solution for methanol, ethanol, 2-propanol and tert-butanol. The experimentally observed inversion of the acidity sequences of these systems is reproduced, and special importance is assigned to the stabilization energy of the conjugate bases in both media.

The SN2 reactions X- + CH3Y → Y- + CH3X have been investigated in the gas phase and in solution using the Hartree−Fock level with 6-31+G* and 3-21G* bases, respectively. In the gas phase the interpretation has been done in the context of the HSAB principle using Gázquez's formalism using the polarizability (proportional to softness) of the two minima corresponding to the two ion−molecule complexes, and the TS, the softness of the nucleophile and the charge on the leaving group. The thermodynamic study shows that the reaction energy, ΔE r - p and the energy differences between the two ion−molecule complexes, ΔE m, are close to the experimental data available. The application of the MHP indicates that in these reactions the molecules arrange themselves to be as hard as possible. The polarizable continuum model (PCM) has been used to study the influence of the solvent on the kinetics of the SN2 reaction. The application of Gázquez's formula provides fundamental information in a case study, with X = Cl and Y = I:  the activation energy calculated with the PCM model yields a very good correlation with the values obtained with Gázquez's formula. Finally, we concentrate on the influence of solvation on the nucleophilicity and the kinetics using the (PCM) model with X = F, I and Y = Br and compare the results with the gas phase. The order of reactivity in the gas phase is F- > I-, which is the same order as in the solvent using the polarizable continuum model, but opposed to experiment. If, however, we take into consideration the interaction energy caused by the hydrogen bond, the order of reactivity in solution is reversed yielding the same results as experiment.

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C-Alkylation and O-alkylation of ethyl acetoacetate by a series of alkylating agents is investigated, in the gas phase as well as in the solvent, within a local viewpoint of the hard and soft acids and bases (HSAB) principle at the Hartree−Fock level using a 3-21+G* basis set. The Gázquez and Méndez formula for calculating the interaction energy is used to reveal the influence of the alkylating agent softness on the two possible orientations in the ethyl acetoacetate alkylation. O-Alkylation was found to be favored by a hard alkylating agent, whereas C-alkylation becomes less and less disfavored upon increasing softness.