Acid anhydrides, acyl chlorides and acylationAQA A-Level Chemistry: Subtopic test

1. 1
   A technician adds ethanoyl chloride, CH₃COCl, in separate experiments to water, to ethanol, to concentrated ammonia and to methylamine, CH₃NH₂. Each reaction is vigorous and produces misty fumes.

   (a)

   Which products form when ethanoyl chloride reacts with water?

   [1 mark]

   • AEthanoic acid and hydrogen chloride
   • BEthanol and chlorine
   • CEthanal and hydrogen chloride
   • DSodium ethanoate and hydrogen

   (b)

   What is the organic product when ethanoyl chloride reacts with methylamine?

   [1 mark]

   • AEthanamide
   • BMethyl ethanoate
   • CEthylamine
   • DN-methylethanamide

   (c)

   Write the equation for the reaction of ethanoyl chloride with ethanol and name the organic product.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Aspirin is made industrially by reacting 2-hydroxybenzoic acid with ethanoic anhydride, (CH₃CO)₂O, rather than with ethanoyl chloride. Both reagents can acetylate the OH group on the benzene ring.

   (a)

   Which statement gives an industrial advantage of ethanoic anhydride over ethanoyl chloride in making aspirin?

   [1 mark]

   • AIt reacts violently with water
   • BIt is cheaper and less corrosive, and reacts less readily with water
   • CIt produces hydrogen chloride as the by-product
   • DIt is a gas at room temperature

   (b)

   What is the other product when 2-hydroxybenzoic acid reacts with ethanoic anhydride?

   [1 mark]

   • AHydrogen chloride
   • BWater
   • CEthanoic acid
   • DEthanol

   (c)

   Give two industrial advantages of using ethanoic anhydride rather than ethanoyl chloride to make aspirin.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A chemist reacts propanoyl chloride, CH₃CH₂COCl, separately with ammonia and with ethylamine, CH₃CH₂NH₂. In each case an amide is formed.

   (a)

   Write the equation for the reaction of propanoyl chloride with ethylamine, name the organic product and name the type of mechanism.

   [3 marks]

   (b)

   Outline the mechanism for the reaction of propanoyl chloride with ammonia, including the movement of electron pairs.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student prepares aspirin (2-ethanoyloxybenzoic acid) by warming 3.00 g of 2-hydroxybenzoic acid (Mr = 138) with excess ethanoic anhydride. The equation is C₇H₆O₃ + (CH₃CO)₂O → C₉H₈O₄ + CH₃COOH. The crude solid is then purified and its purity is checked. The student obtains 2.70 g of pure aspirin (Mr = 180).

   (a)

   The crude aspirin is purified by recrystallisation and its purity is then checked. Describe how the recrystallisation is carried out and how the purity of the product can be checked.

   [6 marks]

   (b)

   Calculate the theoretical yield of aspirin and the percentage yield obtained. Suggest one reason why the percentage yield is less than 100%.

   [6 marks]

   Total for question 4: 12 marks

End of questions