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Carbonyl compounds: aldehydes and ketones

Past-paper questions pack

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Class
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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 · 33 parts · mark schemes follow the questions · www.chemistryaleveltutor.com · Questions and mark schemes © OCR

1. June 2025 · Paper 2 · Q21(b) · 2 marks ·
(b) A chemical test is carried out which gives a positive result for all three compounds. Suggest the reagent and observation of this chemical test. Reagent ............................................................................................................................................ Observation ...................................................................................................................................... [2]
2. June 2025 · Paper 2 · Q21(c) · 3 marks ·
(c) A student is provided with three unlabelled sample tubes, containing either pyruvic acid, methylglyoxal or acetol. The student carries out three chemical tests on each sample. Complete the table with the expected observations, including ‘no change’ where appropriate. Expected observations Chemical test Pyruvic acid Methylglyoxal Acetol Tollens’ reagent .................................... .................................... .................................... .................................... .................................... .................................... Na2CO3(aq) .................................... .................................... .................................... .................................... .................................... .................................... Cr2O7 2–(aq)/H+(aq) .................................... .................................... .................................... .................................... .................................... .................................... [3]
3. June 2025 · Paper 2 · Q21(d) · 4 marks ·
(d) Pyruvic acid reacts with NaBH4. Outline the mechanism for the reaction of pyruvic acid with NaBH4. Include curly arrows and relevant dipoles. O C H3C COOH [4]
4. June 2025 · Paper 2 · Q21(e) · 7 marks ·
(e) Complete the flowchart for the reactions of pyruvic acid. excess NH3 Acyl chloride Compound P reagent(s) ............................................................ O NaOH(aq) O OH Pyruvic acid CH3OH / H2SO4 reagent(s) ............................................................ OH H2 / Ni H2N O OH Compound Q [7]
5. June 2025 · Paper 3 · Q5(a)(v) · 1 marks ·
(v) Suggest why the student heated the mixture from Step 2 with dilute aqueous acid in Step 3. .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [1]
6. June 2024 · Paper 2 · Q19 · 6 marks ·
19* Alkenes and carbonyl compounds take part in addition reactions. Describe one addition reaction of an alkene and one addition reaction of a carbonyl compound. Include reagents and reaction mechanisms. [6] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... Extra answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
7. June 2023 · Paper 2 · Q2 · 1 marks · AO1
2 Which compound reacts with 2,4-dinitrophenylhydrazine but does not react with Tollens’ reagent? A C6H5COCOOH B C6H5CH(OH)CHO C CH3COCHO D CH3CH2CH(OH)CH3 Your answer [1]
8. June 2023 · Paper 2 · Q22(a)(i) · 4 marks · AO1, 2
22 This question is about reactions of acrolein, H2C=CHCHO. (a) Acrolein reacts with sodium cyanide in acidic conditions, NaCN(aq) / H+(aq). (i) Outline the reaction mechanism for this reaction, showing the intermediate and the organic product. The structure of acrolein has been provided. Include curly arrows and relevant dipoles. H H C C H C O H [4]
9. June 2023 · Paper 2 · Q22(a)(ii) · 1 marks · AO1
(ii) Name this type of mechanism. ...................................................................................................................................... [1]
10. June 2023 · Paper 2 · Q22(b) · 9 marks · AO1, 2
(b) Complete the flowchart by filling in each box. reagent(s) ................................... catalyst unsaturated alcohol ................................... diol (major product) reagent(s) ................................... H H reagent(s) C C ................................... H C O H acrolein carboxylic acid reagent(s) ................................... polymer (2 repeat units) acyl chloride [9]
11. June 2023 · Paper 3 · Q3 · 6 marks · AO3
3* A chemist is investigating compound A, shown below, as a potential organic intermediate. O OH CN Compound A Describe the type of stereoisomerism shown by compound A and suggest three reactions of compound A, one for each of the three functional groups using reagents of your choice. In your answer, show stereoisomers of compound A, your chosen reactants and conditions, and the structures for the organic products produced. Mechanisms and equations are not required. 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Additional answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
12. June 2022 · Paper 2 · Q18(a)(i) · 3 marks · AO1
18 This question is about carbonyl compounds. (a) (i) Describe a chemical test to confirm the presence of a carbonyl group. How could the product of this test be used to identify the carbonyl compound? Your answer should not include spectroscopy. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
13. June 2022 · Paper 2 · Q18(a)(ii) · 1 marks · AO1
(ii) Describe a chemical test that would identify whether a carbonyl compound is an aldehyde. Your answer should include the reagent and observations. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1]
14. June 2022 · Paper 2 · Q19(b) · 4 marks · AO2
(b) The structure of 2-hydroxybutanoic acid is shown below. H CH3CH2 C COOH OH 2-hydroxybutanoic acid Fill in the flowchart for reactions involving 2-hydroxybutanoic acid. C6H5COOH / H2SO4 (CH3)2CHOH / H2SO4 reflux reflux H H ............................... CH3CH2 C CN CH3CH2 C COOH OH OH 2-hydroxybutanoic acid NaBH4 [4]
15. June 2022 · Paper 2 · Q21 · 6 marks · AO1, 2
21* Carbon-carbon bond formation is used in synthesis to increase the length of a carbon chain. Describe the formation of carbon–carbon bonds in aliphatic compounds by two different mechanisms. Your answer should include mechanisms for each aliphatic compound. [6] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... Additional answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
16. November 2021 · Paper 2 · Q5 · 1 marks ·
5 2-Methylcyclopentanone, shown below, is reacted with NaCN(aq)/H+(aq) to form an organic product. O CH3 2-methylcyclopentanone Which statement is correct? A In the mechanism, a CN– ion accepts an electron pair. B The mechanism is electrophilic addition. C The organic product has one chiral centre. D The organic product has the molecular formula C7H11NO. Your answer [1]
17. November 2021 · Paper 2 · Q9 · 1 marks ·
9 Which reaction is not a reduction? A C6H5NO2 C6H5NH2 B CH3CN CH3CH2NH2 C CH3CH2Cl CH3CH2NH2 D CH3COCH3 CH3CHOHCH3 Your answer [1]
18. November 2021 · Paper 2 · Q19(a)(ii) · 7 marks · AO1, 2
(ii) Complete the flowchart below for the synthesis of two compounds starting from prenal. O NaBH4 prenal reagent(s): ......................... reagent(s): .............................. catalyst: .............................. reagent(s): ......................... reagent(s): ......................... catalyst: H+ catalyst: H+ O O O O [7]
19. November 2020 · Paper 2 · Q4 · 1 marks · AO2
4 Which compound can be refluxed with acidified potassium dichromate(VI) to form an organic product with molecular formula C5H8O2? A HO O B HO O O HO C O D HO Your answer [1]
20. November 2020 · Paper 2 · Q19(b) · 4 marks · AO2, 3
(b) Describe suitable chemical tests, with observations, that would confirm the presence of the functional groups in F and G. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [4]
21. November 2020 · Paper 2 · Q19(c)(i) · 5 marks · AO1, 2
(c) Compound F reacts with HCN using NaCN(aq) and H+(aq). (i) Outline the mechanism for the reaction of F with NaCN(aq) and H+(aq) and state the name of the mechanism. The structure of F has been provided. Include relevant dipoles, lone pairs and the structure of the organic product. CH3 H CH C H3C C O H2 Name of mechanism: ................................................................................................... [5]
22. November 2020 · Paper 2 · Q21(a) · 5 marks · AO2
21 This question is about organic compounds containing nitrogen. (a) Salt H, (CH3)2CHNH3Cl , is used in the manufacture of garden weedkillers. The flowchart shows the synthesis of the salt H from propanone. Complete the flowchart. Show structures for organic compounds. propanone NaBH4 reagent: ...................................... Br CH H3C CH3 reagent: ...................................... NH3Cl reagent: ...................................... CH H3C CH3 salt H [5]
23. June 2019 · Paper 2 · Q13 · 1 marks · AO1
13 A carbonyl compound is reacted with NaBH4. Which compound(s) could be formed? 1 2-Methylpentan-2-ol 2 2-Methylpentan-1-ol 3 3-Methylpentan-2-ol A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1 Your answer [1]
24. June 2019 · Paper 2 · Q16(b)(i) · 2 marks · AO1
(b) Geraniol and citronellal, shown below, are isomers present in ‘citronella oil’, used as an insect repellent. OH O Geraniol Citronellal • Geraniol and citronellal are structural isomers of each other. • They also show stereoisomerism. (i) Describe how the observations from a chemical test would distinguish between geraniol and citronellal. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
25. June 2019 · Paper 2 · Q18(e)(i) · 6 marks · AO3
(e)* A student intends to synthesise ester C. H O H3C C C O CH3 CH3 Ester C (i) Plan a two-stage synthesis to prepare 12.75 g of ester C starting from 2-methylpropanal, (CH3)2CHCHO. Assume the overall percentage yield of ester C from 2-methylpropanal is 40%. In your answer include the mass of 2-methylpropanal required, reagents, conditions and equations where appropriate. Purification details are not required. [6] ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... Additional answer space if required ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................
26. June 2019 · Paper 2 · Q19(b)(iv) · 7 marks · AO2
(iv) Complete the flowchart for the synthesis of compounds D and E from phenylethanone. H3C O C NaBH4 phenylethanone NaCN(aq) / H+(aq) .................................................. H H C H C .................................................. CH3 compound D Br C CN .................................................. CH3 H2N C COOH .................................... compound E [7]
27. June 2018 · Paper 2 · Q3 · 1 marks ·
3 Which compound does not react with nucleophiles? A CH3CH2CHO B CH3CHCH2 C CH3CH2COCH3 D CH3CH2CH2Cl Your answer [1]
28. June 2018 · Paper 2 · Q20(b)(ii) · 1 marks ·
(ii) Describe a chemical test to confirm that both compounds contain an aldehyde functional group. Your answer should include the reagent and observations. ........................................................................................................................................... ...................................................................................................................................... [1]
29. June 2018 · Paper 2 · Q20(b)(iii) · 3 marks ·
(iii) Describe a chemical test to confirm that cinnamaldehyde and methylcinnamaldehyde contain a carbonyl group. How could the products of this test be used to distinguish between the two compounds? Your answer should not include spectroscopy. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
30. June 2018 · Paper 2 · Q20(c) · 5 marks ·
(c) The flowchart below shows some reactions starting with cinnamaldehyde. Draw the structures of the missing organic compounds in the boxes and add the missing reagent(s) on the dotted line. excess H2/Ni OH CHO reagent(s): .......................... CN cinnamaldehyde NaBH4 H+(aq) [5]
31. June 2018 · Paper 3 · Q6(a)(ii) · 1 marks ·
(ii) What type of reaction has taken place? ...................................................................................................................................... [1]
32. June 2018 · Paper 3 · Q6(a)(iv) · 1 marks ·
(iv) A similar reaction takes place when propanone, (CH3)2CO, is mixed with OH–(aq) ions. Draw the structure of the organic product of this reaction. [1]
33. June 2017 · Paper 2 · Q19(c)(i) · 5 marks ·
(c) Alcohols are important in organic synthesis and can be formed by the reduction of carbonyl compounds. (i) Complete the flowchart by filling in each box. carbonyl compound reduction reagent(s): .......................................... OH NaBr / H2SO4 compound K acid catalyst heat + structural isomers [5]

Mark schemes

1. June 2025 · Paper 2 · Q21(b)
Mark scheme June 2025 Paper 2 Q21(b)
2. June 2025 · Paper 2 · Q21(c)
Mark scheme June 2025 Paper 2 Q21(c)
3. June 2025 · Paper 2 · Q21(d)
Mark scheme June 2025 Paper 2 Q21(d)
4. June 2025 · Paper 2 · Q21(e)
Mark scheme June 2025 Paper 2 Q21(e)
5. June 2025 · Paper 3 · Q5(a)(v)
Mark scheme June 2025 Paper 3 Q5(a)(v)
6. June 2024 · Paper 2 · Q19
Mark scheme June 2024 Paper 2 Q19
7. June 2023 · Paper 2 · Q2
Mark scheme June 2023 Paper 2 Q2
8. June 2023 · Paper 2 · Q22(a)(i)
Mark scheme June 2023 Paper 2 Q22(a)(i)
9. June 2023 · Paper 2 · Q22(a)(ii)
Mark scheme June 2023 Paper 2 Q22(a)(ii)
10. June 2023 · Paper 2 · Q22(b)
Mark scheme June 2023 Paper 2 Q22(b)
11. June 2023 · Paper 3 · Q3
Mark scheme June 2023 Paper 3 Q3
12. June 2022 · Paper 2 · Q18(a)(i)
Mark scheme June 2022 Paper 2 Q18(a)(i)
13. June 2022 · Paper 2 · Q18(a)(ii)
Mark scheme June 2022 Paper 2 Q18(a)(ii)
14. June 2022 · Paper 2 · Q19(b)
Mark scheme June 2022 Paper 2 Q19(b)
15. June 2022 · Paper 2 · Q21
Mark scheme June 2022 Paper 2 Q21
16. November 2021 · Paper 2 · Q5
Mark scheme November 2021 Paper 2 Q5
17. November 2021 · Paper 2 · Q9
Mark scheme November 2021 Paper 2 Q9
18. November 2021 · Paper 2 · Q19(a)(ii)
Mark scheme November 2021 Paper 2 Q19(a)(ii)
19. November 2020 · Paper 2 · Q4
Mark scheme November 2020 Paper 2 Q4
20. November 2020 · Paper 2 · Q19(b)
Mark scheme November 2020 Paper 2 Q19(b)
21. November 2020 · Paper 2 · Q19(c)(i)
Mark scheme November 2020 Paper 2 Q19(c)(i)
22. November 2020 · Paper 2 · Q21(a)
Mark scheme November 2020 Paper 2 Q21(a)
23. June 2019 · Paper 2 · Q13
Mark scheme June 2019 Paper 2 Q13
24. June 2019 · Paper 2 · Q16(b)(i)
Mark scheme June 2019 Paper 2 Q16(b)(i)
25. June 2019 · Paper 2 · Q18(e)(i)
Mark scheme June 2019 Paper 2 Q18(e)(i)
26. June 2019 · Paper 2 · Q19(b)(iv)
Mark scheme June 2019 Paper 2 Q19(b)(iv)
27. June 2018 · Paper 2 · Q3
Mark scheme June 2018 Paper 2 Q3
28. June 2018 · Paper 2 · Q20(b)(ii)
Mark scheme June 2018 Paper 2 Q20(b)(ii)
29. June 2018 · Paper 2 · Q20(b)(iii)
Mark scheme June 2018 Paper 2 Q20(b)(iii)
30. June 2018 · Paper 2 · Q20(c)
Mark scheme June 2018 Paper 2 Q20(c)
31. June 2018 · Paper 3 · Q6(a)(ii)
Mark scheme June 2018 Paper 3 Q6(a)(ii)
32. June 2018 · Paper 3 · Q6(a)(iv)
Mark scheme June 2018 Paper 3 Q6(a)(iv)
33. June 2017 · Paper 2 · Q19(c)(i)
Mark scheme June 2017 Paper 2 Q19(c)(i)