Oxidation of Opened Hemiacetal Rings: Tollen's & Benedict's

[SaintJude]

2. Oxidation of Monosaccharides : The opening of hemiacetal rings allows for oxidation aldose & ketose sugars.

Any hemiacetal group (it has an hydroxyl on the anomeric carbon) will open up and then can be oxided to an "aldonic acid" (has a COOH) Both EK and Kaplan mention Tollen's test and the Benedict's test as a way to detect the occurrence of a carbonyl group oxidizing to COOH (aldehydes& tautomerized ketones)

Read that some SDN member in another thread said they got a question on it in '09. I can't imagine what a question would be like though.Has anyone yet seen a practice question on Tollen's?

Below is a picture of the Benedict's reagent test. So the Cu(OH)2 here the oxidizing agent? Is this in basic or acidic solutions??

View attachment Benedict's Reagant.jpg

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[pfaction]

Cu2O is the oxidizing agent and the sugar is the reducing agent - in this reaction the sugar is a reducing sugar. I have no idea what Tollens is, TPR does not cover it.