JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

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 -OH group is the hemiacetal carbon. In solution, it exists in equilibrium with its open-chain form which contains an aldehyde group: HO-CH_2-CH_2-CH_2-CHO. 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.