Skip to content

Give reasons for the… (Class 12 Chemistry 2026, Q26)

questionbuddy.in/q/cbse-12-chemistry-2026-56-1-1-q26-give-reasons-carboxylic-acids-higher

ChemistryCBSE Class 12 · Board exam 2026, set 56/1/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2026: question 26

Set in the CBSE Class 12 board exam of 2026, paper 56/1/1, section C, question 26, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q26 · 3 marks · Short answerAldehydes, Ketones and Carboxylic Acids

Give reasons for the following :
(a) Carboxylic acids have higher boiling point than alcohols of comparable molecular masses.
(b) Alpha () hydrogens of aldehydes and ketones are acidic in nature.
(c) Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 56/1/1.

Hints

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

Hint 1

How many H-bonds can a –COOH group form compared with an –OH group?

Hint 2

What stabilises the anion formed when an α-H is removed?

Hint 3

What does a strong acid do to the lone pair on nitrogen?

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) Carboxylic acid molecules are held by extensive intermolecular hydrogen bonding. They exist as cyclic dimers even in the vapour phase, so more energy is needed to separate them than for alcohols of similar mass.

    1 mark

  2. (b) The carbonyl group is strongly electron-withdrawing, which weakens the α C–H bond. After loss of , the carbanion (enolate) left behind is resonance-stabilised, with the negative charge shared by the C and O atoms. This makes α-hydrogens acidic.

    1 mark

  3. (c) In strongly acidic medium, the lone pair of ammonia or its derivative () is protonated to . The reagent then loses its nucleophilic character and cannot attack the carbonyl carbon, so a weakly acidic medium (pH about 3.5) is used.

    1 mark

Answer: (a) Extensive intermolecular H-bonding and dimer formation; (b) electron-withdrawing C=O and resonance-stabilised enolate; (c) the nucleophile is protonated in strong acid.

Where the marks are

  • H-bonding / dimer formation in carboxylic acids (1 mark)
  • Electron-withdrawing carbonyl / resonance stabilisation of conjugate base (1 mark)
  • Protonation of the nucleophile in strongly acidic medium (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 paper2026 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.