Reaction Mechanism in Drug Analysis. IV. : Reaction of Xanthine Derivatives with Hydrogen Peroxide and Hydrochloric Acid

One of the methods for determination of caffeine, a xanthine derivative, is decomposition with hydrochloric acid-hydrogen peroxide and with sodium hydroxide, and coloration of the urea derivative thereby formed with a solution of dimethylglyoxime thiosemicarbazide. In order to elucidate the mechanism of the decomposition of caffeine to the urea derivative, caffeine was decomposed with hydrochloric acid and hydrogen peroxide, and the decomposition products were examined from their nuclear magnetic resonance (NMR) and infrared (IR) spectra and from elemental analyses. The products were identified as 8-chlorocaffeine, 1, 3-dimethylparabanic acid, monomethylamine hydrochloride, and tetramethylalloxantine. It was thereby learned that in this method of determination, caffeine is decomposed by hydrochloric acid and hydrogen peroxide to form dimethylparabanic acid via its 8-chloro compound, and the acid is easily decomposed by sodium hydroxide to form the urea derivative which colors with the dimethylglyoxime thiosemicarbazide solution.