Synthetic routes and problem solvingEdexcel International A Level Chemistry: Subtopic test

1. 1
   Compound X has the structure HOCH₂CH=CHCOOH (4-hydroxybut-2-enoic acid). A student has not seen this compound before and is asked to predict its properties from the functional groups it contains.

   (a)

   Which reagent would give effervescence when added to a solution of X?

   [1 mark]

   • ABromine water
   • BAcidified potassium dichromate(VI)
   • C2,4-dinitrophenylhydrazine solution
   • DSodium carbonate solution

   (b)

   Which statement about the isomerism of X is correct?

   [1 mark]

   • AX shows E/Z isomerism because each carbon of the C=C is bonded to two different groups
   • BX shows optical isomerism because it contains a chiral carbon atom
   • CX cannot show any stereoisomerism because it contains a carboxylic acid group
   • DX shows E/Z isomerism because it contains an OH group

   (c)

   Predict whether X is more or less soluble in water than but-2-ene, and explain your answer.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemist wants to make propylamine, CH₃CH₂CH₂NH₂, from bromoethane in two steps. In step 1 bromoethane is converted into a nitrile. In step 2 the nitrile is converted into propylamine.

   (a)

   Which reagent and conditions are used for step 1?

   [1 mark]

   • AAqueous potassium cyanide, heated under reflux
   • BPotassium cyanide dissolved in ethanol, heated under reflux
   • CAmmonia in ethanol, heated in a sealed tube
   • DDilute hydrochloric acid, heated under reflux

   (b)

   Which reagent converts the nitrile into propylamine in step 2?

   [1 mark]

   • ASodium borohydride in water
   • BAcidified potassium dichromate(VI)
   • CLithium tetrahydridoaluminate(III) in dry ether
   • DDilute hydrochloric acid, heated under reflux

   (c)

   A student suggests making propylamine in one step by heating bromoethane with excess ammonia in ethanol. Explain why this cannot work.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A three-step route converts benzene into N-phenylethanamide, C₆H₅NHCOCH₃. Step 1 converts benzene into nitrobenzene (yield 80%). Step 2 converts nitrobenzene into phenylamine (yield 75%). Step 3 converts phenylamine into N-phenylethanamide using ethanoyl chloride (yield 90%). A student starts with 15.6 g of benzene. Relative formula masses: benzene 78.0; N-phenylethanamide 135.0.

   (a)

   Calculate the overall percentage yield and the mass of N-phenylethanamide the student obtains.

   [3 marks]

   (b)

   Suggest the reagents and conditions for each of the three steps, and explain why the temperature of step 1 is carefully controlled.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school technician prepares propanal from propan-1-ol by oxidation with acidified potassium dichromate(VI). Hazard data: propan-1-ol is highly flammable and causes eye damage; propanal is highly flammable and its vapour is harmful and irritating; dilute sulfuric acid is corrosive; potassium dichromate(VI) is oxidising, toxic, carcinogenic and harmful to aquatic life. Boiling temperatures: propanal 49 °C, propan-1-ol 97 °C, propanoic acid 141 °C.

   (a)

   Describe how the technician should carry out the oxidation so that propanal, rather than propanoic acid, is the main product, explaining each choice.

   [6 marks]

   (b)

   Using the hazard data, suggest suitable control measures for this preparation and justify them.

   [6 marks]

   Total for question 4: 12 marks

End of questions