Question

The number of reducing sugars among the following is .......... 

Hint:

A quick rule: If the anomeric carbon has an –OH, it is reducing; if it is OR-linked, it is non-reducing.

Answer 1

Correct Answer: 3

Step 1: Definition of reducing sugars.
A reducing sugar must have a free anomeric carbon capable of mutarotation, meaning it can open to form an aldehyde or keto group.
Step 2: Analyzing each given sugar structure.
Out of the six given structures:
• Any sugar with its anomeric carbon tied in a glycosidic bond is **non-reducing**.
• Any sugar having a free anomeric OH is **reducing**.
On inspecting the structures:
– Three molecules show a free anomeric OH → reducing.
– Three have the anomeric carbon locked in glycosidic linkage → non-reducing.
Step 3: Conclusion.
Thus, the number of reducing sugars among the given molecules is 3.