On the existence of the protonated hydronium dication H4O in sulfolane solution

The enthalpy of solvation in sulfolane of the gaseous protonated hydronium dication is estimated as −628 kcal/mol at 298 K. Using literature data, a value ΔH^o = −212 kcal/mol is calculated for the reaction H₃O⁺ + H⁺→ H₄O²⁺ (in sulfolane), supporting the thermodynamic existence of H₄O²⁺ in sulfolane solution, as characterized previously by potentiometric and conductometric titrations. Some aspects of these results are discussed.