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JEE Main 2025 Jan 29 Shift 1, Chemistry Q19: Properties of Phenol

JEE Main2025Jan 29, Shift 1Chemistry
Q.

The steam volatile compounds among the following are :

Choose the correct answer from the options given below :

  1. A

    (B) and (D) only

  2. B

    (A) and (C) only

  3. C

    (A) and (B) only

  4. D

    (A),(B) and (C) only

Solution

Steam-volatility in substituted phenols/anilines correlates with intramolecular hydrogen bonding (chelation): a chelated molecule is held together within itself and does not form an extended network with neighbours, so it vaporises readily with steam.

The ortho isomers (A) and (B) form internal H-bonds between the donor and the adjacent acceptor, locking the molecule into a six-membered chelate ring and making them steam volatile.

The para isomers (C) and (D) cannot chelate; they instead form intermolecular H-bonds, giving high boiling points and low steam volatility.

Only (A) and (B) are steam volatile.

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