JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

Tollens' reagent is reduced only by an aldehyde or a group in equilibrium with one. Compound C is 2-hydroxytetrahydrofuran, a cyclic hemiacetal whose carbon bears both the ring oxygen and an $-\mathrm{OH}$; it is in equilibrium with the open-chain $\gamma$-hydroxyaldehyde, which reduces $\mathrm{A}{\mathrm{g}}^{+}$ to metallic silver. The 2-methoxy acetal, the 3-methoxy ether and the 3-hydroxy alcohol have no such aldehyde equilibrium and give no reaction. The compound that gives a positive Tollens' test is C.