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I have heard that Schiff's base only gives a positive test for aldehydes. Glucose is an aldehyde. However, I was told that glucose doesn't give a positive Schiff's base test. Is this correct? If so, how?

Melanie Shebel
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Harshal Deshpande
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  • Hello, and welcome to ChemSE. I have completely modified your question, but I retained it's meaning, for it was difficult for other users to understand your question. I hope your question will get reopened soon, and you will get an answer. Good luck! – Pritt says Reinstate Monica Aug 07 '17 at 14:42
  • My bad...My doubt wasn't framed right.. – Harshal Deshpande Aug 07 '17 at 14:49
  • Related: https://chemistry.stackexchange.com/questions/64363/why-do-alpha-hydroxy-ketones-respond-positively-to-tollens-fehlings-benedict https://chemistry.stackexchange.com/questions/40127/why-does-fructose-reduce-tollens-reagent-and-fehlings-solution – Pritt says Reinstate Monica Aug 07 '17 at 16:04

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Schiff test is a colorimetric method for determination of aldehyde groups. Both glucose and fructose are monosaccharides and exhibit oxo-cyclo tautomerism. Glucose is an aldose and has aldehyde group in linear form. Whereas fructose is a ketose and doesn't give a positive Schiff test.

MEL Science
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