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An organic compound (A)… (Class 12 Chemistry 2025, Q33B)

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ChemistryCBSE Class 12 · Board exam 2025, set 56/1/1 · 5 marks · Long answer

CBSE Class 12 Chemistry 2025: question 33(B)

Set in the CBSE Class 12 board exam of 2025, paper 56/1/1, section E, question 33(B), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q33(B) · 5 marks · Long answerAldehydes, Ketones and Carboxylic Acids

An organic compound (A) (molecular formula ) was hydrolysed with dilute sulphuric acid to get a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives But-l-ene. Identify (A), (B) and (C) and write chemical equations for the reactions involved.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 56/1/1.

Hints

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

Hint 1

Hydrolysis of A into an acid and an alcohol tells you A is an ester.

Hint 2

Since oxidising C gives B, the acid and the alcohol have the same carbon skeleton. Split the 8 carbons equally.

Hint 3

Which alcohol gives but-1-ene on dehydration?

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. C dehydrates to but-1-ene, so C is a straight-chain four-carbon primary alcohol. Oxidation of C gives the acid B, so B has the same four-carbon chain. Hence C = butan-1-ol, .

    ½ mark

  2. B = butanoic acid, .

    ½ mark

  3. A () is the ester made from B (4 C) and C (4 C). So A = butyl butanoate, .

    1 mark

  4. Hydrolysis:

    1 mark

  5. Oxidation:

    1 mark

  6. Dehydration:

    1 mark

Answer: A = butyl butanoate (C3H7COOC4H9); B = butanoic acid (C3H7COOH); C = butan-1-ol (C4H9OH)

Where the marks are

  • Identifies A as butyl butanoate (1 mark)
  • Identifies B as butanoic acid (½ mark)
  • Identifies C as butan-1-ol (½ mark)
  • Equation for acid hydrolysis of the ester (1 mark)
  • Equation for chromic acid oxidation of butan-1-ol to butanoic acid (1 mark)
  • Equation for dehydration of butan-1-ol to but-1-ene (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Aldehydes, Ketones and Carboxylic Acids, one at a time, marked against the answer key and marking points.Back to the full paper2025 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.