Question

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

• 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 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:

'D' and 'L' are based on Fischer projections and have no relation to (+) or (-).
Optical rotation (+ or -) is an experimentally determined physical property.
All naturally occurring (+) glucose molecules belong to the D-series.

Answer 1

The Correct Option is B

Step 1: Check the Assertion.
Naturally occurring glucose does rotate plane-polarised light to the right, and this is why it is written as D(+)-glucose. So the Assertion is a true statement.
Step 2: Check the Reason.
The plus sign is indeed the symbol chemists use for dextrorotatory compounds, and the prefix D does refer to configuration, the arrangement of the $-\text{OH}$ group on the reference chiral carbon in the Fischer projection. Both parts of the Reason are individually correct.
Step 3: Check whether the Reason explains the Assertion.
Configuration (D or L) is fixed by comparing the molecule's structure to glyceraldehyde, while optical rotation (+ or -) is a separate, experimentally measured property. One does not follow from the other; some D-sugars are dextrorotatory and others are levorotatory.
Step 4: State the final match.
Both statements are true, but the Reason only defines the symbols, it does not explain why glucose specifically rotates light to the right.
\[ \boxed{\text{Both A and R true, R is not the correct explanation of A}} \]