The acid–base behaviour of phosphoryl and sulphinyl groups in some organic bases

Abstract

The pK_BH⁺ values of benzylmethylphosphine oxide, methyl methylphenylphosphinate (and its para-methyl and para-chloro-derivatives), methyl methanesulphinate, and methyl benzyl sulphoxide have been estimated in H₂SO₄ solutions by an n.m.r. technique. It is suggested that the acid–base behaviour of all the compounds studied is described better by the H_A than by the H₀ acidity function. Structural and substituent effects on basicity are discussed. In the case of methyl methylarylphosphinates different pK_BH⁺ values are obtained by following the change with medium acidity of the CH₃ or of OCH₃ proton resonance chemical shifts. A possible source of this discrepancy is suggested.