Organic Nitrogen Compounds: Amines, Amides, Amino Acids and ProteinsEdexcel International A Level Chemistry: Topic test

1. 1
   Propylamine, CH₃CH₂CH₂NH₂, reacts with ethanoyl chloride, CH₃COCl, at room temperature to give a white solid and fumes of hydrogen chloride.

   (a)

   What is the name of the organic product with the amide functional group?

   [1 mark]

   • APropyl ethanoate
   • BN-ethylpropanamide
   • CPropanamide
   • DN-propylethanamide

   (b)

   Which statement explains why propylamine acts as a base?

   [1 mark]

   • AThe nitrogen atom has a lone pair of electrons that can accept a proton
   • BThe molecule contains a hydroxide ion
   • CThe propyl group is electron-withdrawing, so the nitrogen atom is electron-poor
   • DIt forms hydrogen bonds with water molecules and nothing else

   (c)

   Write the equation for the reaction of propylamine with ethanoyl chloride. Explain why two moles of propylamine are needed for each mole of ethanoyl chloride if the reaction is to go to completion.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Ethylamine, CH₃CH₂NH₂, can be made by heating bromoethane, CH₃CH₂Br, with an excess of ethanolic ammonia in a sealed tube.

   (a)

   Why is an excess of ammonia used?

   [1 mark]

   • AIt acts as a catalyst for the substitution
   • BIt is a stronger acid than ethylamine
   • CA molecule of bromoethane is more likely to meet ammonia than the ethylamine already formed, so further substitution is limited
   • DIt makes the reaction proceed by elimination instead of substitution

   (b)

   Which compound is formed when ethylamine reacts further with bromoethane?

   [1 mark]

   • AEthanamide
   • BDiethylamine
   • CEthanenitrile
   • DN-ethylethanamide

   (c)

   Ethylamine can also be made by reducing ethanenitrile, CH₃CN. State suitable reagents and conditions, and write an equation using [H] to represent the reducing agent.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Poly(propenamide) is made by the addition polymerisation of propenamide, CH₂=CHCONH₂. It is used as a flocculant in water treatment because it dissolves in water. Ar: C = 12.0, H = 1.0, N = 14.0, O = 16.0.

   (a)

   A sample of poly(propenamide) has an average relative molecular mass of 1.42 × 10⁶. Calculate the average number of repeat units in each polymer molecule.

   [3 marks]

   (b)

   Explain, in terms of hydrogen bonding, why poly(propenamide) dissolves in water. State the type of polymerisation and the feature of the monomer that allows it.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Valine, (CH₃)₂CHCH(NH₂)COOH, is an amino acid found in proteins. 6-Aminohexanoic acid, H₂N(CH₂)₅COOH, is a monomer used to make the polyamide nylon-6.

   (a)

   Explain the behaviour of valine as a zwitterion, and describe its form in strongly acidic and in strongly alkaline solutions. Explain why valine is a solid with a high melting temperature rather than a liquid.

   [6 marks]

   (b)

   Valine molecules can join to form a polypeptide. Compare this with the formation of nylon-6 from 6-aminohexanoic acid, explaining the similarities and one difference in the structures of the two polymers.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A polyamide is made by heating pentane-1,5-diamine, H₂N(CH₂)₅NH₂, with hexanedioic acid, HOOC(CH₂)₄COOH.

   (a)

   Which formula is the repeat unit of this polyamide?

   [1 mark]

   • A–[NH(CH₂)₅NH(CH₂)₄CO]–
   • B–[NH(CH₂)₅NHCO(CH₂)₄CO]–
   • C–[NH(CH₂)₅COO(CH₂)₄CO]–
   • D–[NH(CH₂)₅NHCO(CH₂)₆CO]–

   (b)

   What is the relative molecular mass of the small molecule eliminated each time an amide link forms in this reaction?

   [1 mark]

   • A36.5
   • B17.0
   • C44.0
   • D18.0

   (c)

   The polyamide has a much higher melting temperature than poly(ethene). Explain why, in terms of intermolecular forces.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   Serine, HOCH₂CH(NH₂)COOH, and valine, (CH₃)₂CHCH(NH₂)COOH, are both amino acids found in proteins.

   (a)

   A solution of one pure enantiomer of serine rotates the plane of plane-polarised light. Which feature of serine causes this?

   [1 mark]

   • AIt has a chiral carbon atom bonded to four different groups
   • BIt contains an –OH group
   • CIt exists as a zwitterion
   • DIt is a planar molecule

   (b)

   How many different dipeptides can be formed from one molecule of serine and one molecule of valine?

   [1 mark]

   • A1
   • B4
   • C2
   • D3

   (c)

   A sample of serine made in a laboratory from achiral starting materials has no effect on plane-polarised light. Explain why.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A 25.0 cm³ sample of aqueous methylamine, CH₃NH₂, reacts exactly with 21.40 cm³ of 0.100 mol dm⁻³ hydrochloric acid. Ar: C = 12.0, H = 1.0, N = 14.0.

   (a)

   Calculate the concentration of the methylamine solution in mol dm⁻³.

   [3 marks]

   (b)

   (i) Write the equation for the reaction between methylamine and hydrochloric acid, and name the product. [2]
   (ii) Calculate the mass concentration of methylamine in the solution, in g dm⁻³. [2]

   [4 marks]

   Total for question 7: 7 marks

8. 8
   Hexane-1,6-diamine, H₂N(CH₂)₆NH₂, is the monomer used with hexanedioyl dichloride, ClOC(CH₂)₄COCl, to make nylon-6,6. It can be prepared in two steps from 1,4-dibromobutane, BrCH₂CH₂CH₂CH₂Br.

   (a)

   Describe how hexane-1,6-diamine can be prepared from 1,4-dibromobutane. Give the reagents and conditions for each step and an equation for each step.

   [6 marks]

   (b)

   Hexane-1,6-diamine behaves as a base and as a nucleophile. Describe four reactions that show this, with water, with hydrochloric acid, with copper(II) ions and with hexanedioyl dichloride. Include equations or observations.

   [6 marks]

   Total for question 8: 12 marks

End of questions