Question

Which from following tests for glucose confirms presence of carbonyl group?

• A. Action of \(\mathrm{NH}_{2}\mathrm{OH}\) to form oxime
• B. Heating with HI forming \(n\)-hexane
• C. Formation of pentaacetate derivative when reacted with acetic anhydride
• D. Glucose and gluconic acid both form saccharic acid when treated with dilute \(\mathrm{HNO}_{3}\)

Hint:

A test that confirms a carbonyl group must involve a typical nucleophilic addition reaction at C=O.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Aldehydes and ketones react with hydroxylamine to give oximes, which is a characteristic reaction of the carbonyl group.

Step 2: Check each test
Heating with HI giving n-hexane shows a straight six carbon chain.
The pentaacetate shows five hydroxyl groups.
Oxidation with nitric acid to saccharic acid shows a primary alcohol group at the other end.

Step 3: Compare the options
Only the oxime formation with \(\text{NH}_2\text{OH}\) confirms the carbonyl group.

Final Answer:
Oxime formation with hydroxylamine shows that glucose has a carbonyl group. \[ \boxed{\text{(A) }\text{Action of NH}_{2}\text{OH to form oxime}} \]