Reducing Sugar

  1. Fructose is a reducing sugar, and the ketone acts as a reducing centre, which reduces Cu2+ --> Cu+. Therefore fructose itself becomes oxidised.

    However, how can a ketone group be oxidised?

    I thought: aldehyde becomes oxidised to carboxylic acid
    ketone: cannot be oxidised.
  2. jcsd
  3. GCT

    GCT 1,751
    Science Advisor
    Homework Helper

    Try looking up the iodoform reaction.
  4. How does that help. I know the iodoform reaction confirms any 2-one, 2-ol, 2-al, ethanol or ethanal. i.e. CH3C=O, but no hydroxide / iodine for reducing sugar test?
  5. GCT

    GCT 1,751
    Science Advisor
    Homework Helper

    Well, from what I remember, the ketone is reduced in this case to a carboxlic acid, although not completely sure. Try finding the mechanism, I just don't have the time right now.
  6. Yeah, the fructose isomerizes to glucose and mannose via an enediol, which then oxidizes in the standard Benedict's test fashion.

    My students happen to be doing that very experiment today.

    If you want to oxidize an actual ketone, there's always carbonyl oxides...
  7. ok, thank you very much :D
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