Question

Assertion (A): The pentaacetate of glucose does not react with \(H_2N-OH\).
Reason (R): It indicates the presence of free −CHO group in glucose.

• 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:

Hydroxylamine \(H_2N-OH\) reacts with a free aldehyde (\(-CHO\)) group to form an oxime. Whether glucose pentaacetate reacts with it tells us whether a free \(-CHO\) group is available.

Answer 1

The Correct Option is C

Step 1: Understand the test involved.
Hydroxylamine \(H_2N-OH\) reacts only with a free aldehyde \((-CHO)\) or keto group to form an oxime. If a compound does not react, it has no free carbonyl group.

Step 2: Check the Assertion.
Glucose pentaacetate is made by acetylating all five \(-OH\) groups while glucose is in its cyclic form. In this cyclic acetylated form the would-be aldehyde carbon is locked as an acetal, so there is no free \(-CHO\). Hence it does not react with \(H_2N-OH\). The Assertion is TRUE.

Step 3: Check the Reason.
The Reason says this indicates the presence of a free \(-CHO\) group. But not reacting actually shows the ABSENCE of a free \(-CHO\) group. So the Reason is FALSE.

Step 4: Match the statuses.
Assertion is true and Reason is false.

Step 5: Conclude.
The correct option is that Assertion is true but Reason is false, which is option 3.

\[ \boxed{\text{Assertion true, Reason false}} \]