Question

Which of the following is nonreducing sugar?

• A. Option 1
• B. Option 2
• C. Option 3
• D. Option 4

Hint:

Nonreducing sugars have {no free anomeric carbon}. If even one anomeric carbon is free, the sugar will be reducing.

Answer 1

The Correct Option is A

Concept:
A carbohydrate is called a nonreducing sugar
if it does not have a free anomeric carbon. This happens when both anomeric carbons are involved in glycosidic bond formation
.
Step 1: Identify Anomeric Carbon


Anomeric carbon is bonded to two oxygen atoms.
Presence of free \(-OH\) group on this carbon makes the sugar reducing.

Step 2: Analyze Each Option
Option (1):


Both monosaccharide units are linked via their anomeric carbons.
No free anomeric \(-OH\) group is present.
Hence, it is a nonreducing sugar
.
Option (2):


One anomeric carbon remains free.
Hence, it is a reducing sugar
.
Option (3):


Presence of free anomeric \(-OH\) group.
Hence, it is a reducing sugar
.
Option (4):


One anomeric carbon is not involved in glycosidic linkage.
Hence, it is a reducing sugar
.

Final Conclusion:
Only option (1)
represents a nonreducing sugar
.