Reducing Sugar


by garytse86
Tags: reducing, sugar
garytse86
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#1
Apr21-05, 08:40 AM
P: 310
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.
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GCT
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#2
Apr21-05, 10:17 AM
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Try looking up the iodoform reaction.
garytse86
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#3
Apr21-05, 10:20 AM
P: 310
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?

GCT
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#4
Apr21-05, 03:37 PM
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Reducing Sugar


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.
TRCSF
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#5
Apr21-05, 06:37 PM
P: 389
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...
garytse86
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#6
Apr22-05, 01:19 PM
P: 310
ok, thank you very much :D


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