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JEE Main 2026 Jan 23 Shift 1, Chemistry Q18: Preparation of Carboxylic acids

JEE Main2026Jan 23, Shift 1Chemistry
Q.

Compound 'P' undergoes the following sequence of reactions:

'P' is :

  1. A

    1

  2. B

    2

  3. C

    3

  4. D

    4

Solution

Work backwards. The final step is the carbylamine reaction (CHCl/KOH alc): it converts a primary amine into an isocyanide. So the precursor to cyclohexyl isocyanide is cyclohexylamine.

Cyclohexylamine is produced from an amide via the Hofmann bromamide (KOH/Br) rearrangement — the amide loses one carbon and the —C(=O)NH becomes —NH on the adjacent carbon. So Q = cyclohexanecarboxamide.

To reach Q from P via "NH, heat", P must be the carboxylic acid that forms an ammonium salt and then dehydrates to the amide: cyclohexanecarboxylic acid (option 2).

Concept behind this question

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