Patent ID: 6583315
Filing Date: 2003-06-24
Classification: C07F

Abstract:
A process for preparing ethanebis(alkylphosphinic) acids comprising the steps of:a) reacting elemental yellow phosphorus with alkyl halides in the presence of alkali metal hydroxide or of alkaline earth metal hydroxide to give a mixture whose main constituents are the alkali metal salts and/or alkaline earth metal salts of alkylphosphonous, phosphorous, and hypophosphorous acid, b) liberating alkyiphosphonous, phosphorous, and hypophosphorous acid by adding mineral acids, and also at the same time precipitating the alkali metal ions and, respectively, alkaline earth metal ions in the form of their salt of the mineral acids, and then c) esterifying the alkylphosphonous acid from the mixture of the alkylphosphonous, phosphorous, and hypophosphorous acid, d) isolating the ester of alkylphosphonous acid from the mixture and hydrolyzing the same to give alkylphosphonous acid, and e) preparing, from the alkylphosphonous acid, the corresponding ethanebis(alkylphosphinic) acid of the general formula (I) â€ƒwhere R1, and R2 may be identical or different and are hydrogen, a carboxy group, an ester, an alcohol, an unsubstituted or substituted aikyl group having from 1 to 10 carbon atoms, phenyl, benzyl, or alkyl-substituted aromatics, and R3 and R4 are identical or different and are an unsubstituted or substituted alkyl group having from 2 to 20 carbon atoms. in the presense of at least one free radical initiator with alkynes.