Question

An example of non-reducing sugar is

• A. Glucose
• B. Sucrose
• C. Lactose
• D. Maltose

Hint:

All common monosaccharides are reducing. Among disaccharides, sucrose is the most notable non-reducing example.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Reducing sugars are those that have a free aldehydic or ketonic group, which can exist in the form of a hemiacetal or hemiketal. These sugars are capable of reducing reagents like Tollen's reagent or Fehling's solution due to the presence of the free carbonyl group.
Step 2: Detailed Explanation:
1. Glucose: Glucose is a monosaccharide and exists as a cyclic hemiacetal. This free aldehyde group in glucose allows it to act as a reducing sugar, meaning it can reduce Tollen's reagent or Fehling's solution.
2. Maltose and Lactose: Both maltose and lactose are disaccharides, and each has a free hemiacetal group in one of the sugar rings. This free hemiacetal group enables both maltose and lactose to act as reducing sugars.
3. Sucrose: Sucrose is a disaccharide formed by a glycosidic bond between the C1 of glucose and the C2 of fructose. In this case, both the reducing groups (the aldehyde of glucose and the ketone of fructose) are involved in the bond formation, so neither of the sugar rings in sucrose has a free reducing group. As a result, sucrose does not have the ability to reduce reagents like Tollen's or Fehling's solution and is classified as a non-reducing sugar.
Step 3: Final Answer:
Sucrose is the non-reducing sugar.