plumiIsomerism: OCR A‑Level Chemistry B questions
Every OCR A-Level Chemistry B exam question on DF Isomerism (specification points DF(r)–(t)), 2016–2025, with its mark scheme and examiner’s report.
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Q31(b)(iii)
The whole paper ↗![June 2025 Paper 1, question 31(b)(iii): Oleic acid is a cis isomer. Complete the diagram below to show the skeletal formula of the trans isomer of oleic acid. O OH [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-jun25-31-biii-qp.webp?v=3)
Q2(f)(i)
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Q2(f)(ii)
The whole paper ↗
Q34(b)
The whole paper ↗![June 2024 Paper 1, question 34(b): There are other alcohols that are structural isomers of CH3CH2CH(OH)CH3. Draw the skeletal formulae for the two branched‑chain isomers. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-jun24-34-b-qp.webp?v=3)
Q1(a)(i)
The whole paper ↗![June 2024 Paper 2, question 1(a)(i): The side-chains formed by three carboxylic acids are labelled A, B and C. Give the letter of the side-chain that is: Saturated Trans unsaturated [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun24-01-ai-qp.webp?v=3)
Q23(a)(i)
The whole paper ↗![June 2024 AS Paper 1, question 23(a)(i): Draw the skeletal formula of ethanoic acid. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun24-23-ai-qp.webp?v=3)
Q3(g)(i)
The whole paper ↗![June 2024 AS Paper 2, question 3(g)(i): Draw the skeletal formula for the molecule shown below. CH3CH2CH(CH3)CH2CH(CH2CH3)CH(CH3)CH2CH3 [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03302-jun24-03-gi-qp.webp?v=3)
![June 2023 Paper 1, question 13: Which of the following compounds can display E/Z isomerism? A CH2BrCH=CHCH2Br B (CH3CH2)2C=CBr2 C (CH2Br)2C=CH2 D CH2BrCH2BrCH=CH2 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-jun23-13-qp.webp?v=3)
![June 2023 AS Paper 1, question 2: Which of the following exists as cis/trans isomers? A (CH3)2CCHCH3 B CH3CHCHCH3 C CH3CH2CH2CH3 D CH2C(CH3)2 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun23-02-qp.webp?v=3)
Q2(a)
The whole paper ↗![June 2022 Paper 2, question 2(a): Draw the skeletal formula of isomer A and name it. skeletal formula: name: [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun22-02-a-qp.webp?v=3)
Q2(c)(i)
The whole paper ↗![June 2022 Paper 2, question 2(c)(i): Draw the structure of the E isomer of but-2-ene. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun22-02-ci-qp.webp?v=3)
Q2(c)(ii)
The whole paper ↗![June 2022 Paper 2, question 2(c)(ii): Does 2-methylpropene, (CH3)2C=CH2, have E and Z isomers? Explain your answer. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun22-02-cii-qp.webp?v=3)
![June 2022 AS Paper 1, question 17: How many unsaturated structural and E/Z isomers of butene are there? A 3 B 4 C 5 D 6 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun22-17-qp.webp?v=3)
Q1(e)
The whole paper ↗![November 2021 Paper 2, question 1(e): Explain why but-2-ene has two stereoisomers. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-nov21-01-e-qp.webp?v=3)
Q1(d)(i)
The whole paper ↗
Q1(d)(ii)
The whole paper ↗
![November 2020 Paper 1, question 26: How many unsaturated structural isomers are there with the formula C5H10? A 3 B 5 C 6 D 9 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-nov20-26-qp.webp?v=3)
Q4(b)(ii)
The whole paper ↗![November 2020 Paper 2, question 4(b)(ii): Give the systematic name for maleic acid. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-nov20-04-bii-qp.webp?v=3)
Q4(c)
The whole paper ↗![November 2020 Paper 2, question 4(c): Explain why maleic acid and fumaric acid are different compounds. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-nov20-04-c-qp.webp?v=3)
All 36 questions on Isomerism, as a list
- June 2025, Paper 1, Q6 (1 mark): Which of the following pairs can be structural isomers? A acid anhydrides and aldehydes B amines and amides C carboxylic acids and esters D diols and esters You
- June 2025, Paper 1, Q31(b)(iii) (1 mark): Oleic acid is a cis isomer. Complete the diagram below to show the skeletal formula of the trans isomer of oleic acid. O OH [1]
- June 2025, AS Paper 2, Q2(f)(i) (3 marks): There are two unbranched stereoisomers that are unsaturated with the molecular formula C5H10. Draw skeletal formulae for these two stereoisomers and give the sy
- June 2025, AS Paper 2, Q2(f)(ii) (2 marks): There are other branched unsaturated isomers of molecular formula C5H10. Give the name of one of these isomers. State the type of isomerism by which this isomer
- June 2024, Paper 1, Q34(b) (2 marks): There are other alcohols that are structural isomers of CH3CH2CH(OH)CH3. Draw the skeletal formulae for the two branched‑chain isomers. [2]
- June 2024, Paper 2, Q1(a)(i) (1 mark): The side-chains formed by three carboxylic acids are labelled A, B and C. Give the letter of the side-chain that is: Saturated Trans unsaturated [1]
- June 2024, AS Paper 1, Q23(a)(i) (1 mark): Draw the skeletal formula of ethanoic acid. [1]
- June 2024, AS Paper 2, Q3(g)(i) (1 mark): Draw the skeletal formula for the molecule shown below. CH3CH2CH(CH3)CH2CH(CH2CH3)CH(CH3)CH2CH3 [1]
- June 2023, Paper 1, Q13 (1 mark): Which of the following compounds can display E/Z isomerism? A CH2BrCH=CHCH2Br B (CH3CH2)2C=CBr2 C (CH2Br)2C=CH2 D CH2BrCH2BrCH=CH2 Your answer [1]
- June 2023, AS Paper 1, Q2 (1 mark): Which of the following exists as cis/trans isomers? A (CH3)2CCHCH3 B CH3CHCHCH3 C CH3CH2CH2CH3 D CH2C(CH3)2 Your answer [1]
- June 2022, Paper 2, Q2(a) (1 mark): Draw the skeletal formula of isomer A and name it. skeletal formula: name: [1]
- June 2022, Paper 2, Q2(c)(i) (1 mark): Draw the structure of the E isomer of but-2-ene. [1]
- June 2022, Paper 2, Q2(c)(ii) (1 mark): Does 2-methylpropene, (CH3)2C=CH2, have E and Z isomers? Explain your answer. [1]
- June 2022, AS Paper 1, Q17 (1 mark): How many unsaturated structural and E/Z isomers of butene are there? A 3 B 4 C 5 D 6 Your answer [1]
- November 2021, Paper 2, Q1(e) (2 marks): Explain why but-2-ene has two stereoisomers. [2]
- November 2021, AS Paper 2, Q1(d)(i) (1 mark): The groups attached to the carbons in a C=C double bond are in fixed positions because there is no rotation about the C=C bond. Explain why but-2-ene exhibits E
- November 2021, AS Paper 2, Q1(d)(ii) (2 marks): But-2-ene has the molecular formula C4H8. There are two other structural isomers with this molecular formula that are both alkenes. Draw (in the boxes) skeletal
- November 2020, Paper 1, Q26 (1 mark): How many unsaturated structural isomers are there with the formula C5H10? A 3 B 5 C 6 D 9 Your answer [1]
- November 2020, Paper 2, Q4(b)(ii) (2 marks): Give the systematic name for maleic acid. [2]
- November 2020, Paper 2, Q4(c) (2 marks): Explain why maleic acid and fumaric acid are different compounds. [2]
- November 2020, Paper 3, Q2(a)(i) (2 marks): Structure B is described as a ‘cis’ unsaturated oil. Explain the meanings of ‘cis’ and ‘unsaturated’. [2]
- November 2020, AS Paper 2, Q1(a) (1 mark): Draw the skeletal formula of 2-methylbuta-1,3-diene. [1]
- November 2020, AS Paper 2, Q1(c)(ii) (1 mark): The poly(2-chlorobuta-1,3-diene) shown in equation 1.1 is the cis-stereoisomer. Draw the structure of the trans-stereoisomer for poly(2-chlorobuta-1,3-diene). [
- November 2020, AS Paper 2, Q1(c)(iii) (2 marks): Explain how the two stereoisomers for poly(2-chlorobuta-1,3-diene) occur. [2]
- June 2019, AS Paper 2, Q1(d) (2 marks): Another alkene that can be polymerised is but-2-ene, CH3CH=CHCH3. Explain why stereoisomerism can occur in but-2-ene. [2]
- June 2018, AS Paper 1, Q23(c)(i) (1 mark): Draw the skeletal formula for chloroethene. [1]
- June 2018, AS Paper 1, Q23(c)(ii) (1 mark): A student says that chloroethene shows cis-trans isomerism. Is the student correct? Explain your answer. [1]
- June 2018, AS Paper 2, Q2(a) (2 marks): Butanol has the molecular formula, C4H10O. There are four structural isomers with this formula that contain the –OH functional group. Complete the table below t
- June 2017, Paper 1, Q26 (1 mark): What is the correct name of an isomer of pent-1-ene? A cyclopentene B pent-4-ene C 1-methylbut-2-ene D 3-methylbut-1-ene Your answer [1]
- June 2017, Paper 2, Q2(c)(ii) (1 mark): Describe the stereochemistry of the double bonds in AM404. [1]
- June 2017, Paper 2, Q2(c)(iii) (1 mark): Explain how the double bonds in AM404 hold the carbon chain in shape. [1]
- June 2017, Paper 3, Q3(d) (3 marks): Both ocimenol and cinnamyl alcohol molecules show stereoisomerism. OH OH ocimenol cinnamyl alcohol • Name the type of stereoisomerism shown by these molecules.
- June 2017, AS Paper 2, Q2(d) (2 marks): Another substituted alkene is 1-chloroprop-1-ene, shown below H CH3 C C Cl H 1-chloroprop-1-ene Unlike phenylethene, 1-chloroprop-1-ene shows E/Z stereoisomeris
- June 2016, AS Paper 1, Q12 (1 mark): A substance has the formula shown below. CH2 = CCl CH2CH3 Which of the following is a structural isomer of this substance? A 2-chlorobut-1-ene B 3-chlorobut-4-e
- June 2016, AS Paper 1, Q22(b) (1 mark): Isobutylene has a structural isomer that shows E/Z isomerism. Draw the Z isomer. [1]
- June 2016, AS Paper 2, Q1(e) (1 mark): Butane has a structural isomer. Draw the skeletal formula of this isomer and give its systematic name. skeletal formula systematic name [1]
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