Question

Sucrose is classified as a non-reducing sugar because it lacks what specific chemical feature?

• A. Free aldehyde or ketone group
• B. Hydroxyl group
• C. Carbon atom
• D. Glycosidic bond

Hint:

{Reducing sugars} have a free aldehyde or ketone group, while {sucrose is non-reducing} because both reactive groups are involved in the glycosidic bond.

Answer 1

The Correct Option is A

Concept: Sugars are classified as reducing or non-reducing based on their ability to act as reducing agents. Reducing sugars contain a free aldehyde (\(-CHO\)) or ketone (\(C=O\)) group that can participate in redox reactions. Sucrose is a disaccharide composed of glucose and fructose molecules linked together.
Step 1: Structure of sucrose.
In sucrose, glucose and fructose are joined through a glycosidic bond between their anomeric carbons. \[ \text{Glucose} + \text{Fructose} \rightarrow \text{Sucrose} \] This bond blocks the reactive carbonyl groups of both monosaccharides.
Step 2: Absence of a free carbonyl group.
Because the aldehyde group of glucose and the ketone group of fructose are involved in the glycosidic bond, sucrose does not have a free aldehyde or ketone group available to participate in reduction reactions.
Step 3: Conclusion.
Therefore, sucrose is classified as a non-reducing sugar because it lacks: \[ \text{a free aldehyde or ketone group} \]