Solvent Effects on Localized and Delocalized Cationic Charges in Solvolysis<TEX>$^1$</TEX>

A measure of stabilities (-ΔHo) and resonance delocalization (-Δq(Cα+)) for some carbocations has been estimated using the semiempirical AM1 method. The stability (-ΔHo) of carbocations can be correlated with the sensitivity (m) of localized cations to the solvent ionizing power scale Y, whereas the extent of resonance delocalization (-Δq(Cα+)) can be correlated with the sensitivity (h) of delocalized cations to the solvent ionizing power scale Ⅰ. It has been shown that two solvent ionizing power scales Y and I have in general opposite signs so that effects of electrostatic solvation are opposite for the localized and delocalized cationic charges. The use of two different solvent scales for a substrate with delocalizable cationic charge is not only prerequisite to the proper correlation of solvolysis rates but also is justified.