Degradation of (—)-ephedrine in solution and during extraction with diethyl ether

Abstract

Significant losses occurred during the extraction of small quantities of ephedrine from aqueous media using either regular or analytical grades of diethyl ether. The losses were, at least in part, caused by reaction of the ephedrine with aldehydic impurities in the ether; three substituted oxazolidines were identified, using g.l.c. and g.l.c.-ms. These and one other oxazolidine were synthesized and characterized by g.l.c, g.l.c.-ms, nmr and infrared spectroscopy. Alternative mechanisms for ephedrine breakdown were considered. Ephedrine was separately oxidized by three different oxidizing agents and also irradiated by ultraviolet light; the products were characterized by g.l.c, g.l.c.-ms. A method for the purification of diethyl ether is recommended to minimize ephedrine breakdown.