Amines and amidesEdexcel A-Level Chemistry: Subtopic test

1. 1
   Butylamine, CH₃(CH₂)₃NH₂, is a primary aliphatic amine. It dissolves in water to give an alkaline solution and it neutralises dilute hydrochloric acid.

   (a)

   What is the formula of the product formed when butylamine reacts with dilute hydrochloric acid?

   [1 mark]

   • ACH₃(CH₂)₃Cl
   • BCH₃(CH₂)₃NHCOCH₃
   • CCH₃(CH₂)₃NH₃⁺ Cl⁻
   • DCH₃(CH₂)₃OH

   (b)

   Which feature of the butylamine molecule makes it a base?

   [1 mark]

   • AThe lone pair of electrons on the nitrogen atom, which can accept a proton
   • BThe polar N–H bond, which can donate a proton
   • CThe four-carbon chain, which releases hydroxide ions
   • DThe C–N bond, which breaks to form a carbocation

   (c)

   A student adds butylamine dropwise, and then in excess, to aqueous copper(II) sulfate. Describe what is observed and explain the change seen in excess.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student compares the strengths of three bases at 298 K using their pKb values. A lower pKb means a stronger base. Ammonia, NH₃, has pKb = 4.75, butylamine, CH₃(CH₂)₃NH₂, has pKb = 3.39 and phenylamine, C₆H₅NH₂, has pKb = 9.13.

   (a)

   Which list shows the three bases in order of increasing base strength?

   [1 mark]

   • AButylamine < ammonia < phenylamine
   • BAmmonia < butylamine < phenylamine
   • CPhenylamine < butylamine < ammonia
   • DPhenylamine < ammonia < butylamine

   (b)

   Which statement explains why phenylamine is a much weaker base than butylamine?

   [1 mark]

   • APhenylamine has no lone pair of electrons on nitrogen
   • BThe lone pair on nitrogen is delocalised into the benzene ring, so it is less available to accept a proton
   • CThe phenyl group releases electrons towards nitrogen
   • DPhenylamine is insoluble in water, so it cannot accept protons

   (c)

   Explain why butylamine is a stronger base than ammonia.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Primary aliphatic amines can be prepared from halogenoalkanes or by reduction of nitriles. Butylamine, CH₃(CH₂)₃NH₂, can be made from 1-bromobutane, and it can also be made by reducing the nitrile butanenitrile, CH₃CH₂CH₂CN.

   (a)

   State the reagent and conditions for converting 1-bromobutane into butylamine, and explain why a large excess of the reagent is used.

   [3 marks]

   (b)

   Butanenitrile can be converted into butylamine by reduction. Give the reagent and conditions and the equation for the reaction. Explain why catalytic hydrogenation is preferred to the laboratory reagent for large-scale manufacture.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Phenylamine, C₆H₅NH₂, is used to make dyes and is prepared in the laboratory from nitrobenzene, C₆H₅NO₂. Amides such as N-butylethanamide, CH₃CONH(CH₂)₃CH₃, can be made by reacting an amine with an acyl chloride.

   (a)

   Describe how a sample of phenylamine is prepared from nitrobenzene in the laboratory, including the reagents and conditions and the reason for each stage of the procedure.

   [6 marks]

   (b)

   Describe and explain the reaction of ethanoyl chloride with butylamine to make N-butylethanamide. Explain why at least two moles of butylamine are needed for each mole of ethanoyl chloride, and why the amide formed is not basic. State the organic product if ammonia were used instead of butylamine.

   [6 marks]

   Total for question 4: 12 marks

End of questions