The protonation of benzophenones in aqueous sulphuric acid, and the H0 acidity function scale

Abstract

The pK_a values of the conjugate acids of thirteen benzophenones have been determined and used to construct a H₀ acidity scale over the range 40–90% aqueous sulphuric acid. The resonance effects of substituents are much less in evidence than in the corresponding acetophenone and benzaldehyde compounds. Medium effects on the positions of absorption maxima in the ultraviolet spectra of the conjugate acids are recorded.