Abstract Monoethyl esters of 2-quinolylmethylphosphonic acid (3) and 8- quinolylmethylphosphonic acid (6) have been prepared. The corresponding diethyl esters 1 and 4, and sodium salts of monoesters 2 and 5, respectively, have also been isolated. The properties of the monoethyl esters of 8-and 2-quinolylmethylphosphonic acid are very different. While the former was isolated as the hydrochloride, the latter did not form such a ...