Chemistry in superacids. 10. Role of oxonium, sulfonium, and carboxonium dications in superacid-catalyzed reactions

Energies, electronic structures, gas-phase proton affinities, and isodesmic enthalpies (ΔH 0 iso ) of a series of methyl-substitutcd oxonium and sulfonium dications and carboxonium dications (di-O-protonated carbonyl compounds) were calculated using ab initio molecular orbital theory. On the basis of computed energetics, the proton affinities and decomposition barriers were also estimated. The role of dicationic superelectrophiles in a number of superacid-catalyzed reactions is discussed