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Write main product formed… (Class 12 Chemistry 2023, Q27)

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ChemistryCBSE Class 12 · Board exam 2023, set 56/1/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2023: question 27

Set in the CBSE Class 12 board exam of 2023, paper 56/1/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerHaloalkanes and Haloarenes

Write main product formed when :
(a) Methyl chloride is treated with NaI/Acetone.
(b) 2,4,6-trinitrochlorobenzene is subjected to hydrolysis.
(c) n-Butyl chloride is treated with alcoholic KOH.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 56/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

NaI in acetone exchanges one halogen for another.

Hint 2

Electron-withdrawing –NO₂ groups at o/p positions make aryl halides easy to hydrolyse.

Hint 3

Alcoholic KOH removes HCl to form an alkene.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Finkelstein reaction (halogen exchange): . The main product is iodomethane (methyl iodide). NaCl precipitates in acetone, which drives the reaction forward.

    1 mark

  2. (b) Three –NO₂ groups at the ortho and para positions strongly activate the C–Cl bond, so warm water alone hydrolyses it. The product is 2,4,6-trinitrophenol (picric acid):

    1 mark

  3. (c) Alcoholic KOH causes dehydrohalogenation, and only one β-carbon is available:
    . The product is but-1-ene.

    1 mark

Answer: (a) CH₃I (iodomethane); (b) picric acid (2,4,6-trinitrophenol); (c) CH₃CH₂CH=CH₂ (but-1-ene)

Where the marks are

  • (a) Iodomethane (1 mark)
  • (b) Picric acid / 2,4,6-trinitrophenol (1 mark)
  • (c) But-1-ene (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Haloalkanes and Haloarenes, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 56/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.