Question

Which of the following statement(s) is/are correct about the given compound?

• A. It exhibits ring-chain tautomerism.
• B. It forms osazone with phenylhydrazine.
• C. It gives eight (8) stereoisomers.
• D. It responds to Tollen's reagent.

Hint:

Remember that all aldohexoses like glucose, galactose, and mannose have 4 chiral carbons, yielding 16 stereoisomers in total. Since they are reducing sugars, they all give positive Tollen's, Fehling's, and Benedict's tests, and undergo osazone formation.

Answer 1

The Correct Option is B, C, D

Step 1: Understanding the Concept:
The structure shown is D-glucose, an aldohexose. We need to evaluate its chemical reactivity and stereochemistry. Glucose is a reducing sugar that exists in an equilibrium between its open-chain form and two cyclic hemiacetal forms (pyranoses).
Step 2: Detailed Explanation:
- Statement (A): Correct. In aqueous solution, glucose undergoes ring-chain tautomerism (mutarotation) where the open chain form is in equilibrium with $\alpha$-D-glucopyranose and $\beta$-D-glucopyranose.
- Statement (B): Correct. Like all monosaccharides with a free carbonyl or hemiacetal group, glucose reacts with three equivalents of phenylhydrazine to form a yellow crystalline osazone (glucosazone).
- Statement (C): Incorrect. The open chain form of glucose has 4 chiral centers. The total number of stereoisomers for an aldohexose is $2^n = 2^4 = 16$. This includes 8 D-isomers and 8 L-isomers. Glucose is just one of these 16.
- Statement (D): Correct. Glucose is a reducing sugar because it possesses a hemiacetal group that easily converts to an aldehyde in solution. It reduces Tollen's reagent (ammoniacal silver nitrate) to a metallic silver mirror.
Step 3: Final Answer:
Statements (A), (B), and (D) are correct.