SOLVENT EFFECTS ON LOCALIZED AND DELOCALIZED CATIONIC CHARGES IN SOLVOLYSIS

A measure of stabilities (-Delta H-0) and resonance delocalization (-D elta q(C-alpha(+))) for some carbocations has been estimated using the semiempirical AM1 method. The stability (-Delta H-0) of carbocations can be correlated with the sensitivity (m) of localized cations to the solvent ionizing power scale Y, whereas the extent of resonance deloc alization (-Delta q (C-alpha(+))) can be correlated with the sensitivi ty (h) of delocalized cations to the solvent ionizing power scale I. I t has been shown that two solvent ionizing power scales Y and I have i n general opposite signs so that effects of electrostatic solvation ar e opposite for the localized and delocalized cationic charges. The use of two different solvent scales for a substrate with delocalizable ca tionic charge is not only prerequisite to the proper correlation of so lvolysia rates but also is justified.