Examples of reducing sugars

This model allows you to study the structure of glucose, fructose and maltose molecules. A reducing sugar is any sugar that is capable of acting as a reducing agent because it has a free aldehyde group or a free ketone group. All monosaccharides, as well as some disaccharides, oligosaccharides and polysaccharides, are reducing sugars. Sugar containing aldehyde groups is oxidized to carboxylic acids. Common test reagents are Benedict's reagent (CuSO4 / citrate) and Fehlings' reagent (CuSO4 / tartrate). Sugar is classified as a reducing sugar because it reduces C u 2+ to C u +, which forms a red precipitate, copper (I) oxide.