Baljet reaction
Chemical reagent for testing cardenolides
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The Baljet reaction is a qualitative and quantitative method of analysis published by Henri Baljet[1] in 1918.[2] This chemical reaction is used for the detection and colorimetric[3] determination of cardenolides. To the sample, an aqueous hydroxide solution and an ethanolic picric acid solution is combined and added, with a positive test turning orange or red.[4][5][better source needed] The mechanism involves cardenolides 1 reacting in alkaline solution with picric acid 2 to form stabilized Meisenheimer complexes, as shown with the resonance form 3a to 3c:
