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Determination of purine bases. I. The determination of theophylline and 7-hydroxyethyltheophylline in anhydrous medium and their basic dissociation constants

K. Linek and C. Peciar

Slovak Academy of Sciences, Bratislava

 

Abstract: The basicity of theophylline (I) and 7-hydroxyethyltheophylline (II), as expressed by the dissocn. consts. of their conjugated acids was detd. spectrophotometrically. The pK value for I was 0.5 at 25° and for II 0.0 at 25°. A titration method based on the titration with HClO4 in Ac2O medium involved a Ag electrode as the indicator for the potentiometric detn. of the equivalence point. Acetylation decreases the basicity of I so that 2 potential jumps appear in the titration curve, corresponding to I and II, resp. Without acetylation, I and II cannot be distinguished because their dissocn. consts. are too close. I and II can also be detd. by detn. of total base by HClO4 titration, and then in another sample, by detn. of I by the argentometric method, which is not affected by II. 25 references.

Full paper in Portable Document Format: 169a692.pdf (in Slovak)

 

Chemical Papers 16 (9) 692–700 (1962)

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