JEE Main 2026 — Biomolecules Question with Solution
JEE Main 2026 (24 January Shift 1)
Question
A student is given one compound among the following compounds that gives positive test with Tollen's reagent.
The compound is :
The compound is :
Choose an option
Show full solutionCorrect option: D
Correct answer
DC
Step-by-step explanation
Tollen's reagent is a mild oxidizing agent that gives a positive test (silver mirror) with aldehydes and -hydroxy ketones.
In cyclic structures, hemiacetals are in equilibrium with their open-chain hydroxy-aldehyde forms in aqueous solution, whereas acetals and ethers are stable and do not open up.
Compound A is a cyclic acetal (specifically a methyl glycoside type structure). It is stable and does not show Tollen's test.
Compound B is a cyclic ether with a methoxy group at a non-anomeric position. It is stable.
Compound C is a cyclic hemiacetal. The carbon attached to both the ring oxygen and the group is the hemiacetal carbon. In solution, it exists in equilibrium with its open-chain form which contains an aldehyde group: . Therefore, it gives a positive Tollen's test.
Compound D is a cyclic ether with an alcohol group at a non-anomeric position. It does not have a hemiacetal linkage and will not give a positive Tollen's test.
Thus, the correct compound is C.
In cyclic structures, hemiacetals are in equilibrium with their open-chain hydroxy-aldehyde forms in aqueous solution, whereas acetals and ethers are stable and do not open up.
Compound A is a cyclic acetal (specifically a methyl glycoside type structure). It is stable and does not show Tollen's test.
Compound B is a cyclic ether with a methoxy group at a non-anomeric position. It is stable.
Compound C is a cyclic hemiacetal. The carbon attached to both the ring oxygen and the group is the hemiacetal carbon. In solution, it exists in equilibrium with its open-chain form which contains an aldehyde group: . Therefore, it gives a positive Tollen's test.
Compound D is a cyclic ether with an alcohol group at a non-anomeric position. It does not have a hemiacetal linkage and will not give a positive Tollen's test.
Thus, the correct compound is C.
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