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(I) Write the IUPAC… (Class 12 Chemistry SQP 2026-27, Q27A)

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ChemistryCBSE Class 12 · Sample paper, session 2026-27 · 3 marks · Short answer

CBSE Class 12 Chemistry sample paper 2026-27: question 27(A)

From the official CBSE sample question paper for 2026-27, section C, question 27(A), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27(A) · 3 marks · Short answerHaloalkanes and Haloarenes

(I) Write the IUPAC name of the following compound (1)

(II) When reacts with AgCN and KCN, Compound “X” and “Y” respectively are formed. Identify “X” and “Y”. Support your answer with appropriate reason. (2)

Figure in the paper: Benzene ring with a Br substituent and, at the adjacent (ortho) position, a sec-butyl group: CH(CH3)-CH2CH3. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

Name the side chain CH(CH₃)CH₂CH₃ as a substituent and give Br and that group the lowest locants.

Hint 2

is ambident: it can attack through C or through N.

Hint 3

Consider whether the cyanide salt is ionic or covalent.

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. (I) 1-Bromo-2-(butan-2-yl)benzene, also written as 1-bromo-2-(1-methylpropyl)benzene.

    1 mark

  2. X (with AgCN) = , propyl isocyanide.

    ½ mark

  3. Y (with KCN) = , butanenitrile (propyl cyanide).

    ½ mark

  4. KCN is ionic and gives free ions. This ambident nucleophile attacks through carbon, the more nucleophilic site, so a C–C bond forms and the product is the nitrile.

    ½ mark

  5. AgCN is mainly covalent (Ag–C bond), so only the nitrogen lone pair is free to attack. A C–N bond forms, giving the isocyanide.

    ½ mark

Answer: (I) 1-Bromo-2-(butan-2-yl)benzene; (II) X = CH₃CH₂CH₂NC, Y = CH₃CH₂CH₂CN

Where the marks are

  • Correct IUPAC name (1 mark)
  • X = propyl isocyanide (½ mark)
  • Y = butanenitrile (½ mark)
  • Ionic KCN attacks through C (½ mark)
  • Covalent AgCN attacks through N (½ 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 paperSample paper 2026-27: 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.