Mesoionic compounds. Part III. Acid-catalysed hydrolysis and protonation behaviour of 4,5-diphenylisosydnone

Abstract

The hydrolysis of 4,5-diphenylisosydnone has been studied in aqueous solutions of mineral acids. For perchloric, sulphuric, and hydrobromic acids, plots of the first-order rate coefficient k₁ against [H⁺] show maxima which are caused by extensive protonation of the substrate. The protonation behaviour of 4,5-diphenylisosydnone has been studied and correlates better with the amide acidity function, H_A, than with H₀.