[Distribution of carbenicillin, benzylpenicillin and phenylmalonic acid in an organic solvent-water system].

Distribution of carbenicillin, benzylpenicillin and phenylmalonic acid in butyl acetate-water and methylene chloride-water systems within wide ranges of pH of the aqueous phase was studied. The experimental data were reviewed taking into account the distribution between the phases of the compound molecules and dissociation of the acids in the aqueous solution. The distribution constants of the compound molecules were calculated to be 37 (the literature data), 11.6 and 5.2 for every antibiotic respectively in the first system and 10 and 0.24 for carbenicillin and benzylpenicillin in the second system (the value for phenylmalonic acid was not calculated). When the concentration of carbenicillin in butyl acetate is high, dimerization of the acid molecule in the nonaqueous phase should be taken into the account. The dimerization constant is equal to 16.6 M-1.