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Organic synthesis and practical techniques (Module 4)

Past-paper questions pack

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Questions are numbered; the mark schemes (the answer key) follow on separate pages so the question pages can be handed out alone. www.chemistryaleveltutor.com

OCR AS and A-level Chemistry past-paper questions since 2016 · 27 parts · mark schemes follow the questions · www.chemistryaleveltutor.com · Questions and mark schemes © OCR

1. June 2025 · AS Paper 2 · Q3(c) · 2 marks ·
(c) The structure of malic acid is shown below. OH H HOOC C C COOH H H When malic acid is heated with an acid catalyst, a mixture of cis and trans stereoisomers is produced. Draw the structures of the cis and trans isomers. cis trans [2]
2. June 2025 · Paper 2 · Q4 · 1 marks ·
4 Which diagram shows the correct way to set up apparatus for converting ethanol to ethanoic acid? water out water in A B water in water out water out water in water in water out C D Your answer [1]
3. June 2025 · AS Paper 2 · Q5(c) · 6 marks ·
(c)* 2-Chlorobutane, CH3CH2CHCl CH3, is an organic liquid with a boiling point of 70 °C. A student prepares 2-chlorobutane from butan-2-ol, CH3CH2CHOHCH3, as shown in the equation below. CH3CH2CHOHCH3 + NaCl + H2SO4 CH3CH2CHCl CH3 + NaHSO4 + H2O The student’s method is outlined below. • Add 9.25 g CH3CH2CHOHCH3 to an excess of NaCl (aq) in a pear-shaped flask. • Add an excess of concentrated sulfuric acid. • Heat the flask under reflux for about 45 minutes. The student obtains a reaction mixture containing an organic layer (density = 0.87 g cm–3) and an aqueous layer (density = 1.00 g cm–3). After purification, the percentage yield of CH3CH2CHCl CH3 is 65.0 %. Describe how the student could obtain a pure, dry sample of CH3CH2CHCl CH3 from the reaction mixture and explain the reason for carrying out each purification step. Calculate the mass of pure CH3CH2CHCl CH3 that would be expected from this preparation. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6] Extra answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
4. June 2025 · AS Paper 2 · Q5(d)(i) · 3 marks ·
(d) Haloalkanes are important intermediates in organic synthesis. A student plans a two-stage synthesis to prepare compound Z from a hydrocarbon alkene X. (i) Draw the structure of the hydrocarbon alkene X in the box and write down the reagents for each stage on the dotted lines. Alkene X Stage 1 .................................. Br Br H CH3 H H C C C C C H H H H H H Compound Y Stage 2 .................................. OH OH H CH3 H H C C C C C H H H H H H Compound Z [3]
5. June 2025 · AS Paper 2 · Q6(b)(ii) · 2 marks ·
(ii) Identify two functional groups which are likely to be present in Compound B but are not present in Compound A. Explain your answers. Functional group .............................................................................................................................. .......................................................................................................................................................... .......................................................................................................................................................... Explanation ...................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... [2]
6. June 2025 · Paper 2 · Q17 · 6 marks ·
17* This question is about an organic synthesis. A student plans a two-stage synthesis of compound F from compound D, as shown below. Cl OH OH O Stage 1 Stage 2 Compound E Compound D Compound F Plan a two-stage synthesis for the preparation of 2.50 g of compound F from compound D. The overall percentage yield of compound F from compound D is 31.5%. In your answer include the mass of compound D required, reagents and equations for each step. 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7. June 2025 · Paper 2 · Q19(b)(ii) · 4 marks ·
(ii) The reaction to form 1-bromopropane from propan-1-ol is carried out in a flask. After the reaction, the flask contains a mixture of an organic layer (density = 1.35 g cm–3) and an aqueous layer (1.04 g cm–3). Describe how to obtain pure 1-bromopropane from the mixture. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [4]
8. June 2024 · AS Paper 1 · Q18 · 1 marks ·
18 Which functional groups are present in the compound below? O O OH A Alcohol and aldehyde. B Alcohol and ketone. C Carboxylic acid and aldehyde. D Carboxylic acid and ketone. Your answer [1]
9. June 2024 · AS Paper 1 · Q25(c) · 2 marks ·
(c) Primary alcohols can be oxidised under distillation to make aldehydes. Draw a labelled diagram to show how you would set up apparatus for distillation. [2]
10. June 2024 · Paper 2 · Q5 · 1 marks ·
5 Geraniol, shown below, is a component in many natural oils. OH Geraniol Which pair of reagents identifies both functional groups in geraniol? A Acidified dichromate(VI) and 2,4-dinitrophenylhydrazine. B Bromine water and 2,4-dinitrophenylhydrazine. C Bromine water and acidified dichromate(VI). D Tollens’ reagent and aqueous silver nitrate in ethanol. Your answer [1]
11. June 2024 · Paper 2 · Q23(d) · 4 marks ·
(d) Describe how to purify the impure compound H from the two layers in Step 2. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [4]
12. June 2023 · AS Paper 1 · Q18 · 1 marks · AO2
18 A student has planned the two-stage synthesis shown below. H OH OH H3C C C Intermediate H3C C C H H3C H CH3 H Which compound could be the intermediate for this synthesis? H H A H3C C C H CH3 H Br H B H3C C C H CH3 H OH H C H3C C C H CH3 H Br Br D H3C C C H CH3 H Your answer [1]
13. June 2023 · Paper 3 · Q5(b)(i) · 2 marks · AO3
(b) Aspirin reacts with hot NaOH(aq), under reflux. (i) Draw a labelled diagram of suitable apparatus for reflux. [2]
14. June 2022 · AS Paper 2 · Q1(d) · 2 marks · AO2
(d) Other fruits contain different organic acids. Apple juice contains malic acid which has the following structure. H OH HOOC C C COOH H H Malic acid can be oxidised by heating with acidified potassium dichromate(VI). Write a balanced equation for the reaction, showing the structure of the organic product. Use [O] to represent the oxidising agent. [2]
15. June 2022 · AS Paper 2 · Q5(c)(ii) · 3 marks · AO3
(ii) The student mixes butan-2-ol, sodium bromide and sulfuric acid in a pear-shaped flask, and refluxes the mixture. After 1 hour, the mixture in the flask has separated into two layers: an aqueous layer and an organic layer. Describe the procedures the student would need to carry out to obtain a pure, dry sample of 2-bromobutane from this mixture. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
16. June 2022 · Paper 3 · Q3(a) · 6 marks · AO2, 3
3 Information about 1-bromobutane and butan-1-ol is shown in the table. Compound Melting point / °C Boiling point / °C Density / g cm–3 1-bromobutane –113 102 1.268 butan-1-ol –90 118 0.810 A student prepares a sample of 1-bromobutane by refluxing 9.25 g of butan-1-ol with sodium bromide and sulfuric acid. After reflux, the reaction mixture is purified. The student obtains 6.10 cm3 of pure 1-bromobutane. (a)* Draw a diagram to show how the student would have carried out the reflux and calculate the percentage yield of 1-bromobutane that the student obtains. Describe how the student could have obtained pure 1-bromobutane from the reaction mixture obtained after reflux. 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17. November 2021 · AS Paper 1 · Q24(c)(ii) · 2 marks · AO3
(ii) Draw a labelled diagram to show how you would set up apparatus for reflux. [2]
18. November 2021 · AS Paper 2 · Q7(b) · 6 marks · AO1, 2, 3
(b)* The student’s method for the preparation is outlined below. • Add 10.0 cm3 (7.70 g) of (CH3)3COH and 30 cm3 concentrated hydrochloric acid (an excess) to a round-bottom flask. Stopper the flask. • Shake the flask until the mixture separates into two layers. Densities: (CH3)3CCl : 0.85 g cm–3; concentrated HCl : 1.18 g cm–3 After purification, the percentage yield of (CH3)3CCl is 76%. Explain how the student could obtain a pure, dry sample of (CH3)3CCl from the mixture in the flask and calculate the mass of pure (CH3)3CCl that would be expected from this preparation. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Additional answer space if required. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [6]
19. November 2020 · Paper 2 · Q20(a) · 6 marks · AO2, 3
20 Cyclopentanol can be reacted to form cyclopentene. Cyclopentene is a liquid with a boiling point of 44 °C and a density of 0.74 g cm−3. A student plans to prepare 4.00 g of cyclopentene by reacting cyclopentanol (boiling point 140 °C) with an acid catalyst. Equation OH + H2O The expected percentage yield of cyclopentene is 64.0%. Method The student carries out the preparation using apparatus set up for distillation, as shown below. 1 The reaction mixture is heated gently, and a distillate containing impure cyclopentene is collected. cyclopentanol and water concentrated out phosphoric acid water in water bath distillate ice-water mixture 2 The distillate has an aqueous layer and an organic layer. The student purifies the cyclopentene from the distillate. (a)* Calculate the mass of cyclopentanol that the student should use and explain how pure cyclopentene could be obtained from the distillate. [6] ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Additional answer space if required ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................
20. November 2020 · Paper 3 · Q1(a)(i) · 2 marks · AO1
1 This question is about organic chemistry. (a) This part is about two practical techniques used in organic preparations. (i) Complete the missing labels on the diagram and name the technique. ......................................... ...................................................... ......................................... ...................................................... Heat Name of technique: ...................................................................................................... [2]
21. June 2019 · AS Paper 2 · Q5(b)(i) · 6 marks · AO2, 3
(b) Hex-1-ene is a liquid with a boiling point of 63 °C and a density of 0.67 g cm–3. Hex-1-ene can be prepared by refluxing hexan-1-ol (boiling point 157 °C) with an acid catalyst. Hexan-1-ol is a liquid with a boiling point of 157 °C and a density of 0.82 g cm–3. The equation is shown below. + H2O OH After reflux, the resulting mixture contains unreacted hexan-1-ol, hex-1-ene and water. The mixture is then purified. The expected percentage yield of hex-1-ene from hexan-1-ol is 62.5%. (i)* A student plans to prepare 4.20 g of hex-1-ene by this method. Calculate the mass of hexan-1-ol that the student should use and explain how you could obtain pure hex-1-ene from the mixture obtained after reflux. [6] ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... Additional answer space if required ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................
22. June 2018 · AS Paper 2 · Q5(a)(i) · 6 marks ·
5 (a) 1-Bromobutane is an organic liquid with a boiling point of 102 °C. A student prepares 1-bromobutane by reacting butan-1-ol with sulfuric acid and sodium bromide. The student boils the mixture for one hour. The equation is shown below. CH3CH2CH2CH2OH + H+ + Br – CH3CH2CH2CH2Br + H2O The student obtains a reaction mixture containing an organic layer (density = 1.27 g cm–3) and an aqueous layer (density = 1.00 g cm–3). (i)* Draw a labelled diagram to show how you would safely set up apparatus for the preparation. Outline a method to obtain a pure sample of 1-bromobutane from the reaction mixture. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [6]
23. June 2018 · Paper 2 · Q19(c)(i) · 2 marks ·
(c) A student hydrolyses a haloalkane, E, using the following method. • 0.0100 mol of haloalkane E is refluxed with excess NaOH(aq) to form a reaction mixture containing an organic product F. • The reaction mixture is neutralised with dilute nitric acid. • Excess AgNO3(aq) is added to the reaction mixture. 1.88 g of a precipitate G forms. Organic product, F, has a molar mass of 74.0 g mol−1 and has a chiral carbon atom. (i) Draw a labelled diagram to show how the student would carry out the hydrolysis of haloalkane E. [2]
24. June 2017 · AS Paper 2 · Q4(c) · 6 marks ·
(c)* Describe the oxidation reactions of butan-1-ol forming an aldehyde and a carboxylic acid. Explain, using a diagram, how the aldehyde can be produced in the laboratory by controlling the reaction conditions. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [6]
25. June 2017 · AS Paper 2 · Q6(a)(i) · 2 marks ·
6 Organic compounds can be prepared in the laboratory using synthetic routes with two or more stages. (a) A student devises a two-stage synthesis of cyclohexene from bromocyclohexane. Br Step 1 Step 2 Intermediate E NaOH(aq) bromocyclohexane cyclohexene (i) Suggest the structure of intermediate E and the reagent(s) and conditions for step 2. reagent(s) and conditions .............................................................................................. [2]
26. June 2016 · AS Paper 1 · Q26(c)(ii) · 3 marks · AO3
(ii) A student plans a two-stage synthesis for preparing compound F from compound B. The synthesis first prepares compound E, as shown in the flowchart. Draw the structure of compound E in the box and state the reagents for each stage on the dotted lines. H CH3 ......................... C C stage 1 H CH3 Compound B Compound E stage 2 ......................... H CH3 HO C C OH H CH3 Compound F [3]
27. June 2016 · AS Paper 2 · Q6(c)(ii) · 2 marks · AO3
15 (ii) A student plans to carry out this oxidation using the apparatus shown in the diagram. Give one reason why the apparatus is not suitable and describe a more suitable way of carrying out this oxidation. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]

Mark schemes

1. June 2025 · AS Paper 2 · Q3(c)
Mark scheme June 2025 Paper 2 Q3(c)
2. June 2025 · Paper 2 · Q4
Mark scheme June 2025 Paper 2 Q4
3. June 2025 · AS Paper 2 · Q5(c)
Mark scheme June 2025 Paper 2 Q5(c)
4. June 2025 · AS Paper 2 · Q5(d)(i)
Mark scheme June 2025 Paper 2 Q5(d)(i)
5. June 2025 · AS Paper 2 · Q6(b)(ii)
Mark scheme June 2025 Paper 2 Q6(b)(ii)
6. June 2025 · Paper 2 · Q17
Mark scheme June 2025 Paper 2 Q17
7. June 2025 · Paper 2 · Q19(b)(ii)
Mark scheme June 2025 Paper 2 Q19(b)(ii)
8. June 2024 · AS Paper 1 · Q18
Mark scheme June 2024 Paper 1 Q18
9. June 2024 · AS Paper 1 · Q25(c)
Mark scheme June 2024 Paper 1 Q25(c)
10. June 2024 · Paper 2 · Q5
Mark scheme June 2024 Paper 2 Q5
11. June 2024 · Paper 2 · Q23(d)
Mark scheme June 2024 Paper 2 Q23(d)
12. June 2023 · AS Paper 1 · Q18
Mark scheme June 2023 Paper 1 Q18
13. June 2023 · Paper 3 · Q5(b)(i)
Mark scheme June 2023 Paper 3 Q5(b)(i)
14. June 2022 · AS Paper 2 · Q1(d)
Mark scheme June 2022 Paper 2 Q1(d)
15. June 2022 · AS Paper 2 · Q5(c)(ii)
Mark scheme June 2022 Paper 2 Q5(c)(ii)
16. June 2022 · Paper 3 · Q3(a)
Mark scheme June 2022 Paper 3 Q3(a)
17. November 2021 · AS Paper 1 · Q24(c)(ii)
Mark scheme November 2021 Paper 1 Q24(c)(ii)
18. November 2021 · AS Paper 2 · Q7(b)
Mark scheme November 2021 Paper 2 Q7(b)
19. November 2020 · Paper 2 · Q20(a)
Mark scheme November 2020 Paper 2 Q20(a)
20. November 2020 · Paper 3 · Q1(a)(i)
Mark scheme November 2020 Paper 3 Q1(a)(i)
21. June 2019 · AS Paper 2 · Q5(b)(i)
Mark scheme June 2019 Paper 2 Q5(b)(i)
22. June 2018 · AS Paper 2 · Q5(a)(i)
Mark scheme June 2018 Paper 2 Q5(a)(i)
23. June 2018 · Paper 2 · Q19(c)(i)
Mark scheme June 2018 Paper 2 Q19(c)(i)
24. June 2017 · AS Paper 2 · Q4(c)
Mark scheme June 2017 Paper 2 Q4(c)
25. June 2017 · AS Paper 2 · Q6(a)(i)
Mark scheme June 2017 Paper 2 Q6(a)(i)
26. June 2016 · AS Paper 1 · Q26(c)(ii)
Mark scheme June 2016 Paper 1 Q26(c)(ii)
27. June 2016 · AS Paper 2 · Q6(c)(ii)
Mark scheme June 2016 Paper 2 Q6(c)(ii)