Q. 13.43 - An Introduction to General, Organic, and Biological Chemistry

Question

Indicate whether each disaccharide in the problem $13.41$is a reducing sugar or not.

Step-by-Step Solution

Answer

Structure (a) in $13.41$ is, $\beta$-lactose. It contains free aldose groups, so it is a reducing sugar. Structure (b) in $13.41$ is, $\alpha$-maltose. It is also a reducing sugar as it contains free aldose group.

Step 1: Introduction.

A disaccharide is a sugar that is generated when two monosaccharides are linked together by a glycosidic bond. 

Disaccharides, like monosaccharides, are simple sugars that dissolve in water. Sucrose, lactose, and maltose are three frequent examples. Disaccharides are one of four chemical groups that make up carbohydrates.

Step 2: Given Information.

Is the disaccharide a reducible sugar or not.

Step 3: Explanation.

Because the aldose group in monosaccharides may diminish the Benedict's reagent, they are referred to as reducing sugars. Because ketones tautomerize to aldoses in a solution, they also reduce sugars. 

Disaccharides can be reduced or non-reduced sugars, whereas monosaccharides are always reduced sugars.

If the sample is a reducing sugar, the cupric ions are reduced to cuprous ions, resulting in the formation of cuprous oxide and a positive Benedict's reaction. 

Aldoses, on the other hand, are not accessible with polysaccharides.