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JEE Main 2026 Jan 24 Shift 1, Chemistry Q14: Properties and Important Reactions of Aldehydes & Ketones

JEE Main2026Jan 24, Shift 1Chemistry
Q.

A student is given one compound among the following compounds that gives positive test with Tollen's reagent.

The compound is :

  1. A

    D

  2. B

    A

  3. C

    B

  4. D

    C

Solution

Tollen's reagent gives a positive test with aldehydes (and easily oxidisable groups). Hemiacetals (a carbon bearing both -OR and -OH on a ring carbon) exist in equilibrium with their open-chain aldehyde form and therefore reduce Tollen's reagent.

Structure C is a cyclic hemiacetal: ring oxygen and a hydroxyl group on the same carbon. It opens to an open-chain hydroxy-aldehyde, which is then oxidised by Tollen's reagent to give the silver mirror.

The methoxy-substituted analogues (A, B) and the simple tetrahydrofuran-derived structure D are acetals/ethers and do not undergo this equilibrium — no positive test.

Compound C is correct.

Concept behind this question

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