Question

Assertion (A): D (+)-Glucose is dextrorotatory.
Reason (R): Symbol ‘D’ represents its dextrorotatory nature.

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

Hint:

Remember: D/L is about configuration, +/– is about optical rotation direction.

Answer 1

The Correct Option is C

Step 1: D (+)-Glucose is indeed dextrorotatory — it rotates plane-polarized light to the right. So, Assertion (A) is true.
Step 2: However, the ‘D’ in D-glucose does not represent its optical activity. ‘D’ refers to its configuration relative to D-glyceraldehyde (it tells about the position of the –OH group on the chiral carbon farthest from the aldehyde group).
Step 3: The sign (+) or (–) indicates optical rotation, while ‘D’ and ‘L’ indicate configuration only. So the Reason (R) is false.