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Q: Dragendroff’s reagent does not give a positive test with
  • A. Caffeine
  • B. Morphine
  • C. Codeine
  • D. Emetine
Correct Answer: Option A - Dragendroff's reagent does not give positive test with caffeine. Caffeine bongs to xanthines which in turn belong to alkaloids. When the Dragendroff's reagent is used, the presence of an alkaloid is indicated by formation of red brown precipitate. Pure caffeine is white ,while crude caffeine is nearly pale yellow. Alkaloid, if present in the solution of sample, will react with Dragendroff's reagent and produce an orange or orange - red precipitate morphine, codeine emetine give orange red precipitale.
A. Dragendroff's reagent does not give positive test with caffeine. Caffeine bongs to xanthines which in turn belong to alkaloids. When the Dragendroff's reagent is used, the presence of an alkaloid is indicated by formation of red brown precipitate. Pure caffeine is white ,while crude caffeine is nearly pale yellow. Alkaloid, if present in the solution of sample, will react with Dragendroff's reagent and produce an orange or orange - red precipitate morphine, codeine emetine give orange red precipitale.

Explanations:

Dragendroff's reagent does not give positive test with caffeine. Caffeine bongs to xanthines which in turn belong to alkaloids. When the Dragendroff's reagent is used, the presence of an alkaloid is indicated by formation of red brown precipitate. Pure caffeine is white ,while crude caffeine is nearly pale yellow. Alkaloid, if present in the solution of sample, will react with Dragendroff's reagent and produce an orange or orange - red precipitate morphine, codeine emetine give orange red precipitale.