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

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

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

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

(I) What is the IUPAC nomenclature of the compound: $(C H_{3})_{3} C - C (C H_{3}) B r - C H_{2} C H_{3}$ (1)

(II) Which of the following will be hydrolysed more readily?
$C H_{2} = C H - C H_{2} C l$ or $(C H_{3})_{2} C H C l$
Support your answer with reason. (2)

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

Draw out (CH₃)₃C– fully to find the longest chain.

Hint 2

Compare the stability of the carbocations each halide would form.

Hint 3

Can the positive charge be delocalised in either cation?

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.

(I) Longest chain: $C H_{3} - C (C H_{3})_{2} - C (B r) (C H_{3}) - C H_{2} - C H_{3}$ (5 C). Numbering from the left gives locants 2,2,3,3, which are lower than the alternative. Name: 3-Bromo-2,2,3-trimethylpentane.
1 mark
(II) $C H_{2} = C H - C H_{2} C l$ (allyl chloride) is hydrolysed more readily than $(C H_{3})_{2} C H C l$ .
1 mark
Hydrolysis goes through a carbocation (SN1). Allyl chloride gives the allyl cation, which is resonance-stabilised: $C H_{2} = C H - C + H_{2} \leftrightarrow C + H_{2} - C H = C H_{2}$ , with the positive charge spread over two carbons. The 2° isopropyl cation $(C H_{3})_{2} C H^{+}$ has no such resonance and is less stable.
1 mark

Answer: (I) 3-Bromo-2,2,3-trimethylpentane; (II) Allyl chloride, because its carbocation is resonance-stabilised.

Where the marks are

Correct IUPAC name (1 mark)
Identifies allyl chloride (1 mark)
Resonance stabilisation of the allyl carbocation compared with the 2° carbocation (1 mark)

Revise the chapter

Chapter: Haloalkanes and Haloarenes (notes, formulas, where marks are lost and every past question)

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.

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

Hints

Step-by-step solution

Revise the chapter

More questions from Haloalkanes and Haloarenes