Simulation · Chemistry · Class 12

Which sugar reduces Tollens' reagent?

From the lesson Disaccharides and the glycosidic link in Biomolecules. Change the values and watch what happens.

The idea behind it

NCERT §10.1.3

Two monosaccharides join by losing a water molecule, leaving an oxide bridge between them. A link between sugar units through oxygen is a glycosidic linkage. Dilute acid or enzymes hydrolyse it back.
If both reducing groups (the aldehydic or ketonic carbons) are used up in the link, the disaccharide is non-reducing. If one stays free it is reducing.
Sucrose: C1 of α-D-glucose joined to C2 of β-D-fructose. Both reducing carbons are in the bond, so sucrose is a non-reducing sugar.
Sucrose is dextrorotatory. Its hydrolysis gives equal moles of D-(+)-glucose (+52.5°) and D-(–)-fructose (–92.4°). Fructose's laevorotation is the larger, so the mixture is laevorotatory.
The sign of rotation flips from (+) to (–) on hydrolysis; the product is called invert sugar.
Maltose: two α-D-glucose units, C1 of one joined to C4 of the other. The second unit's C1 can open to a free aldehyde in solution, so maltose is reducing.
Lactose (milk sugar): β-D-galactose and β-D-glucose linked from C1 of galactose to C4 of glucose. The glucose unit's C1 can give a free aldehyde, so lactose is reducing.

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