Question:medium

Observe the following reactions: I. D-Glucose \(\xrightarrow{NH_2OH}\) II. D-Glucose \(\xrightarrow[(ii) NH_2OH]{(i) (CH_3CO)_2O}\). Correct statement regarding the reactions I and II is:

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Acetylation protects the reactive carbonyl groups of monosaccharides from further nucleophilic addition.
Updated On: Jun 9, 2026
  • Oxime is formed in both the reactions I, II
  • Oxime is not formed in both the reactions I, II
  • Oxime is formed in reaction I but oxime is not formed in reaction II
  • Oxime is not formed in reaction I but oxime is formed in reaction II
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The Correct Option is C

Solution and Explanation

Step 1: Recall what makes an oxime.
Hydroxylamine $NH_2OH$ reacts with a free carbonyl group such as the aldehyde $-CHO$ of glucose to give an oxime. So a free aldehyde must be available for an oxime to form.
Step 2: Look at reaction I.
In reaction I, plain D-glucose meets $NH_2OH$. Glucose has a free $-CHO$ group (in its open chain form), so it readily forms glucose oxime.
Step 3: Conclude for reaction I.
So an oxime IS formed in reaction I.
Step 4: Look at reaction II.
Here glucose is first treated with acetic anhydride $(CH_3CO)_2O$. This acetylates the hydroxyl groups and locks glucose in its cyclic acetylated form, so the aldehyde group is no longer free.
Step 5: Apply the oxime rule to reaction II.
With the carbonyl now blocked, $NH_2OH$ has nothing to react with, so NO oxime forms in reaction II.
Step 6: Combine the two results.
Oxime forms in reaction I but not in reaction II.
\[ \boxed{\text{Oxime is formed in reaction I but oxime is not formed in reaction II}} \]
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