Abstract (o-Hydroxyphenyl) methylphosphonic acids are readily obtained from o- (bromomethyl)-or o-(hydroxymethyl) phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pK a values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.
