Relationship between superelectrophilicity and the electrophilicity index of isolated species.

We report a relationship between the superelectrophilicity of a series of dications and the electrophilicity index of isolated species. The enhanced electrophilicity is described by global and local reactivity indexes. Alkyloxonium and carboxonium dications and diprotonated carboxylic acids have been used as simple benchmark systems to discuss this relationship on a qualitative and quantitative basis. The theoretical scale of electrophilicity roughly reproduces the experimental superelectrophilicity hierarchy established on the basis of the (17)O and (13)C NMR chemical shifts in alkyloxonium and carboxonium ions and diprotonated carboxylic acids.