Question

Assertion (A): D(+)-Glucose is dextrorotatory in nature.
Reason (R): (+) represents dextrorotatory nature and D represents its configuration.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

{Important Distinction:} D/L → Configuration (structure) (+)/(–) → Optical activity (experimentally observed) D does NOT always mean dextrorotatory.

Answer 1

The Correct Option is A

The question involves the distinction between the terms "dextrorotatory" and "D-configuration" in the context of glucose. Let us explore this in detail:

1. Understanding D(+)-Glucose:
   • D(+)-Glucose is a specific type of glucose molecule. Here, the notation D and (+) have distinct meanings.
   • D-Configuration: This refers to the orientation of the hydroxyl group (-OH) on the chiral carbon farthest from the aldehyde or keto group in the molecule. In a Fischer projection, it appears on the right-hand side. The 'D' configuration is part of the stereochemical description and does not indicate optical activity.
   • (+)-Notation: This indicates that the compound is dextrorotatory. When a compound is dextrorotatory, it means that it rotates plane-polarized light to the right or clockwise.
2. Assertion and Reason Analysis:
   • Assertion (A): "D(+)-Glucose is dextrorotatory in nature." This is true because the (+) indicates that glucose rotates plane-polarized light to the right.
   • Reason (R): "(+) represents dextrorotatory nature and D represents its configuration." This is also true as explained above; (+) does reflect its dextrorotatory nature and D signifies the configuration related to its stereochemistry.
3. Conclusion and Correct Option:
   • The reason correctly explains the assertion because it accurately attributes the dextrorotatory nature to the notation (+) and configuration to 'D'.
   • The correct option is: "Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)." This is the correct conclusion drawn from the understanding of the terms used in the description of D(+)-Glucose.

By understanding these notations clearly, one can accurately determine the optical activity and configuration properties of various sugar molecules.