JEE Main 2026 · 23 January · morning · Single correct · +4 / −1
From the given following (A to D) cyclic structures, those which will not react with Tollen's reagent are:
- (a) A and D
- (b) A and B
- (c) B and D
- (d) B and C
Answer and solution
Answer (d) B and C
Solution
Chemistry ma’am · 3 steps
Look at the carbon beside the ring oxygen: free OH means the ring opens, OCH₃ means it stays shut.
- What Tollens needs. Tollens' reagent oxidises a free -CHO group. A cyclic sugar reacts only if its ring can open back into the open-chain aldehyde.
- Hemiacetal versus acetal. Find the anomeric carbon, the ring carbon bonded to the ring oxygen that also carries H and one more O group. If that group is -OH, the carbon is a hemiacetal, and the ring opens in solution to give the aldehyde. If that group is -OCH₃, the carbon is an acetal (a glycoside), and the ring cannot open, so there is no free aldehyde.
Structure Group on anomeric carbon Type Reacts with Tollens? A (six-membered ring) -OH hemiacetal yes B (six-membered ring) -OCH₃ acetal (glycoside) no C (five-membered ring) -OCH₃ acetal (glycoside) no D (six-membered ring) -OH hemiacetal yes - So. B and C are methyl glycosides. They are locked in the ring and give no silver mirror, so the answer is (d).
The idea to keep. A cyclic sugar is reducing only when its anomeric carbon carries a free OH (hemiacetal). Once that OH becomes OR, as in a glycoside, the ring is locked and Tollens' and Fehling's tests are negative.
Answer from the NTA final answer key. Solution by PrepWiser.