Question

Hydrolysis of sucrose gives :

• A. \(\alpha\)-D-(–)-Glucose and \(\beta\)-D-(–)-Fructose
• B. \(\alpha\)-D-(+)-Glucose and \(\beta\)-D-(–)-Fructose
• C. \(\alpha\)-D-(+)-Glucose and \(\alpha\)-D-(–)-Fructose
• D. \(\alpha\)-D-(–)-Glucose and \(\alpha\)-D-(+)-Fructose

Hint:

Remember the components of the three common disaccharides: - Sucrose \(\rightarrow\) Glucose + Fructose - Lactose \(\rightarrow\) Glucose + Galactose - Maltose \(\rightarrow\) Glucose + Glucose The sign of optical rotation ((+) for dextro, (–) for levo) is an experimental property and must be memorized for common sugars like glucose (+) and fructose (–).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We are asked to identify the specific products, including their stereochemistry and optical rotation, obtained from the hydrolysis of sucrose.
Step 2: Detailed Explanation:
1. Composition of Sucrose:
Sucrose is a common disaccharide. It is formed by a glycosidic bond between two monosaccharides: \(\alpha\)-D-glucose and \(\beta\)-D-fructose. The linkage connects the anomeric carbon of glucose (C-1) to the anomeric carbon of fructose (C-2).
2. Hydrolysis Reaction:
Hydrolysis, which can be catalyzed by an acid (like HCl) or an enzyme (like invertase or sucrase), breaks the glycosidic bond. This releases the two constituent monosaccharides.
\[ \text{Sucrose} + \text{H}_2\text{O} \xrightarrow{\text{Hydrolysis}} \text{D-Glucose} + \text{D-Fructose} \] 3. Stereochemistry and Optical Rotation of Products:
- The glucose unit is released as \(\alpha\)-D-glucose. D-glucose is dextrorotatory, meaning it rotates plane-polarized light to the right. This is indicated by a (+) sign. So, the product is \(\alpha\)-D-(+)-glucose. (In solution, it undergoes mutarotation to an equilibrium mixture of \(\alpha\) and \(\beta\) forms, but the initial product is the \(\alpha\)-anomer).
- The fructose unit is released as \(\beta\)-D-fructose. D-fructose is levorotatory, meaning it rotates plane-polarized light to the left. This is indicated by a (–) sign. So, the product is \(\beta\)-D-(–)-fructose.
4. Conclusion:
The hydrolysis of sucrose yields an equimolar mixture of \(\alpha\)-D-(+)-glucose and \(\beta\)-D-(–)-fructose. Comparing this with the given options, option (B) is the correct choice.
Step 3: Final Answer:
Hydrolysis of sucrose gives \(\alpha\)-D-(+)-glucose and \(\beta\)-D-(–)-fructose.