Amines: properties and reactionsEdexcel International A Level Chemistry: Subtopic test

1. 1
   A technician is preparing 0.10 mol dm⁻³ solutions of ethylamine, CH₃CH₂NH₂, ammonia and phenylamine, C₆H₅NH₂, so that their behaviour with water can be compared. Ethylamine is a gas at room temperature that dissolves freely in water to give an alkaline solution.

   (a)

   Which equation correctly shows ethylamine behaving as a base in water?

   [1 mark]

   • ACH₃CH₂NH₂ + H₂O ⇌ CH₃CH₂NH⁻ + H₃O⁺
   • BCH₃CH₂NH₂ + H₂O ⇌ CH₃CH₂NH₃⁺ + OH⁻
   • CCH₃CH₂NH₂ + H₂O ⇌ CH₃CH₂OH + NH₃
   • DCH₃CH₂NH₂ + OH⁻ ⇌ CH₃CH₂NH₃⁺ + O²⁻

   (b)

   Which row lists the three compounds in order of increasing basicity?

   [1 mark]

   • Aammonia < ethylamine < phenylamine
   • Bethylamine < ammonia < phenylamine
   • Cphenylamine < ammonia < ethylamine
   • Dphenylamine < ethylamine < ammonia

   (c)

   Explain why ethylamine is miscible with water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Butylamine, CH₃CH₂CH₂CH₂NH₂, is used by a pharmaceutical company as a starting material. It is converted into a range of nitrogen-containing products by reacting it with different organic reagents.

   (a)

   Butylamine reacts with ethanoyl chloride. Which organic compound is formed?

   [1 mark]

   • ACH₃CONHCH₂CH₂CH₂CH₃, N-butylethanamide
   • BCH₃COOCH₂CH₂CH₂CH₃, butyl ethanoate
   • CCH₃COO⁻ ⁺H₃NCH₂CH₂CH₂CH₃, butylammonium ethanoate
   • DCH₃CH₂CH₂CONHCH₂CH₃, N-ethylbutanamide

   (b)

   Butylamine is heated with bromoethane. What type of reaction takes place in the first step?

   [1 mark]

   • AElectrophilic substitution
   • BNucleophilic addition
   • CFree-radical substitution
   • DNucleophilic substitution

   (c)

   Write an equation, using structural formulae, for the reaction of butylamine with ethanoyl chloride, and name the organic product.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Phenylamine, C₆H₅NH₂, is a primary aromatic amine used in the manufacture of dyes. A student compares phenylamine with butylamine by measuring the pH of separate solutions of the same concentration and finds that the butylamine solution has the higher pH.

   (a)

   Explain why phenylamine is a much weaker base than butylamine.

   [3 marks]

   (b)

   Phenylamine is only slightly soluble in water but dissolves in dilute hydrochloric acid. Write an equation for the reaction with hydrochloric acid, explain why the phenylamine dissolves, and state how phenylamine can be regained from the solution.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student investigates the reactions of amines. In one experiment aqueous butylamine is added a little at a time to aqueous copper(II) sulfate. In a second experiment butylamine is heated with an excess of bromoethane.

   (a)

   Aqueous butylamine is added a little at a time to aqueous copper(II) sulfate until it is in excess. Describe what is seen and explain the changes, with equations where appropriate.

   [6 marks]

   (b)

   Describe, in words, the mechanism of the first step of the reaction between butylamine and bromoethane, and explain why a mixture of products is obtained when bromoethane is in excess.

   [6 marks]

   Total for question 4: 12 marks

End of questions