| 摘要 |
The invention relates to a process for preparing ethanebis(alkylphosphinic) acids bya) 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 alkylphosphonous, 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 thenc) 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, ande) preparing, from the alkylphosphonous acid, the corresponding ethanebis(alkylphosphinic) acid of the general formula (I) where R1 and R2 may be identical or different and are hydrogen, a carboxy group, a carboxylic acid derivative, an unsubstituted or substituted alkyl 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, by free-radical-initiated reaction with alkynes, and also to the use of the ethanebis(alkylphosphinic) acids prepared by this process as starting material for preparing flame retardants and precursors for the synthesis of other phosphorus-containing compounds.
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