Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Methylphosphinediacetic acid, a novel carboxyphosphine ligand, was obtained as the hydrochloride after reacting methyldichlorophosphine with ethyl bromozinc acetate, subjecting the ester formed to basic hydrolysis, and treating the disodium salt with excess hydrochloric acid. The substance was characterized by its analytical and spectral data. The protonation of the anion demonstrated that the methyl group, with low electronic and steric demands, induces a pronounced increase in the basicity of the phosphorus atom as compared with hitherto examined phosphineacetic acids: the first proton bonds exclusively to the phosphorus (pK = 6.19), whereas protonation of the carboxyl groups only occurs in acid solutions (pK = 2.76 and 1.2, respectively); hence, the free acid has the zwitterion structure.