The acid–base behaviour of phosphoryl and sulphinyl groups in some organic bases
Abstract
The pKBH+ 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 HA than by the H0 acidity function. Structural and substituent effects on basicity are discussed. In the case of methyl methylarylphosphinates different pKBH+ 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.