Process for preparing free alpha-hydroxy acids from ammonium salts thereof

摘要

A process for preparing alpha -hydroxy acids by heating ammonium salts of alpha -hydroxy acids of general formula (I), removing the formed ammonia and water, adding water to the residue, and heating the obtained mixture, wherein R is hydrogen, C1 -C6 alkyl, alkyl(C1 -C6)thioalkyl(C1 -C6), phenyl or the like. This process is freed from the problem of disposal of by-products such as ammonium bisulfate and makes it possible to prepare a free alpha -hydroxy acid from an ammonium salt thereof economically and in a high yield.