Question

Name the sugar present in sugarcane. What are the hydrolysis products of this sugar? Is this sugar a reducing sugar?

Hint:

Sucrose = Glucose + Fructose (linked via both anomeric carbons). No free $-$CHO or $-$CO group $\rightarrow$ non-reducing.

Answer 1

Step 1: Sugar in sugarcane.
The sugar in sugarcane is sucrose, a disaccharide with molecular formula $C_{12}H_{22}O_{11}$.
Step 2: Hydrolysis products.
Hydrolysis by dilute acid or the enzyme invertase gives: $C_{12}H_{22}O_{11} + H_2O \rightarrow C_6H_{12}O_6\,(\text{D-glucose}) + C_6H_{12}O_6\,(\text{D-fructose})$.
Step 3: Is sucrose a reducing sugar?
No. In sucrose, the anomeric $C_1$ of glucose and anomeric $C_2$ of fructose are both involved in the glycosidic bond. There is no free anomeric $-OH$ to open into a free $-CHO$ or $-CO$ group, so sucrose cannot reduce Tollen's or Fehling's reagent.
Step 4: Conclusion.
Sugar in sugarcane: sucrose. Hydrolysis gives D-glucose + D-fructose. Sucrose is a non-reducing sugar.