Question

An example of non-reducing sugar is

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

Hint:

A reducing sugar has a free aldehyde or ketone group (a free anomeric carbon) that can reduce Tollen's or Fehling's reagent.

Answer 1

The Correct Option is B

Step 1: Meaning of reducing sugar.
A reducing sugar has a free aldehyde or ketone group (a free anomeric carbon) that can reduce Tollen's or Fehling's reagent.

Step 2: Check glucose.
Glucose has a free aldehyde group, so it is a reducing sugar.

Step 3: Check lactose and maltose.
In both lactose and maltose, one anomeric carbon is still free, so they too are reducing sugars.

Step 4: Check sucrose.
In sucrose, the anomeric carbons of both glucose and fructose are tied up in the glycosidic linkage. No free aldehyde or ketone group is left, so it cannot reduce these reagents.

Step 5: Conclusion.
Sucrose is the non-reducing sugar.

Answer: Sucrose.