OCR A-Level Chemistry AS Breadth in chemistry (01), June 2023: Question 17

1 mark · Medium difficulty · Multiple Choice

Identify the organic product formed when 3-methylcyclohexanol is reacted with NaBr and H2SO4.

Practise this question

Question

Multiple choice question showing the reaction of 3-methylcyclohexanol with NaBr and H2SO4, with four options A, B, C, and D representing different haloalkane or alkene structures containing a six-membered ring and a methyl group.
Question text

17 3-Methylcyclohexanol is reacted with NaBr and H2SO4.

What is the organic product?

BrBr

Br

Br

A

BrBr

Br

Br

B

C

D

Your answer [1]

Mark scheme

Show the mark scheme The mark scheme shows that the correct answer for question 17 is option A.

17 A 1 AO2.5

How to answer it

Reaction of 3-Methylcyclohexanol with NaBr and H₂SO₄

What this question tests

This question assesses your knowledge of the chemical reactions of alcohols, specifically the nucleophilic substitution (halogenation) of a secondary alcohol to form a haloalkane using a sodium halide and concentrated sulfuric acid ( NaBr / H₂SO₄ ). It tests your ability to identify functional group transformations and interpret skeletal formulas containing substituent positions and stereochemical isomerism.

Question 17

Exam Breakdown & Solutions

✅ Correct Answer: A

The correct organic product is A (1-bromo-3-methylcyclohexane / 3-methylcyclohexyl bromide).

Mark Awarded: 1 / 1 mark (AO2.5 - Applying chemical knowledge)

💡 Key Knowledge

  • Reagent Generation: NaBr and H₂SO₄ react in situ to produce hydrogen bromide ( HBr ).
  • Functional Group Change: The alcohol ( -OH ) group on the secondary carbon is replaced by a halogen ( -Br ) atom.
  • Positional Integrity: The methyl group position remains fixed at carbon-3 relative to the newly substituted bromine atom.

🧠 Exam Technique

Trace the carbon skeleton carefully. 3-Methylcyclohexanol has the -OH group on carbon-1 and the methyl group on carbon-3 (or vice-versa depending on numbering). Substitution replaces the -OH with -Br without shifting the methyl branch or creating an alkene elimination product under standard halogenation conditions.

❌ Common Errors

  • Elimination Confusion (C & D): Mistaking substitution conditions for dehydration conditions (which would form alkenes like cyclohexene derivatives).
  • Positional Isomerism (B): Incorrectly shifting the methyl group directly opposite the bromine atom (para-relationship), failing to maintain the correct original substitution pattern of the 3-methyl ring.

Topics

Module 4: Core organic chemistry · Module 6: Organic chemistry and analysis · 4.2 Alcohols, haloalkanes and analysis · 6.2 Nitrogen compounds, polymers and synthesis

Question and mark scheme from the OCR A-Level Chemistry examination, AS Breadth in chemistry (01), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.