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CAIE A Level Chemistry 33.1 Carboxylic Acids

Practise preparing and oxidising carboxylic acids, forming acyl chlorides and comparing acid strengths, using equations and reagent conditions to distinguish related reactions.

Syllabus
2028–2030
Course
Chemistry 9701
Level
A2

Exam points

  • prepare benzoic acid by side-chain oxidation and form acyl chlorides with chlorinating agents
  • recognise further oxidation of methanoic and ethanedioic acids from products and test observations
  • explain acidity trends through electron withdrawal, distance and stabilisation of the carboxylate ion

Covered syllabus points

33.1.1—Preparation of benzoic acid33.1.2—Carboxylic acids to acyl chlorides33.1.3—Oxidation of carboxylic acids33.1.4—Acidities of carboxylic acids, phenols33.1.5—Acidities of chlorine-substituted carboxylic

33.1 Carboxylic acids question 1

[Maximum number: 1]

Benzophenone can be synthesised from benzoic acid in two steps as shown.

In step 1 compound J, a reactive reaction intermediate, is formed.
Compound J then reacts with an organic compound, K, to form benzophenone.

benzoic acid

benzoic acid

Suggest reagents and conditions for step 1.

33.1 Carboxylic acids question 2

[Maximum number: 6]

Fig. 6.1 shows two reactions of ethanedioic acid, HOOCCOOH .

Fig. 6.1

Fig. 6.1

Question (a)

(a)

Draw the organic product G in the box in Fig. 6.1.

[ 1 ]

Question (b)

(b)

In Fig. 6.1, SOCl2\mathrm{SOCl}_{2} is given as the reagent that reacts with HOOCCOOH to produce G.

Identify a different reagent that also reacts with HOOCCOOH to produce G.

[ 1 ]

Question (c)

(c)

Identify two different reagents that oxidise HOOCCOOH to form carbon dioxide and water.

[ 2 ]

Question (d)

(d)

HOOCCOOH ionises as shown.

HOOCCOOH⇌HOOCCOO−+H+\mathrm{HOOCCOOH} \rightleftharpoons \mathrm{HOOCCOO}^{-}+\mathrm{H}^{+}

HOOCCOOH is a much stronger acid than methanoic acid, HCOOH .

Suggest an explanation for this difference in acidity.

[ 2 ]
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