OCR A-Level Chemistry Synthesis and analytical techniques (02), November 2021: Question 9

1 mark · Medium difficulty · Multiple Choice

Identify which reaction among four given organic transformations is not a reduction process.

Practise this question

Question

Multiple choice question 9 asks which of the four listed reactions is not a reduction. Option A shows C6H5NO2 converting to C6H5NH2, option B shows CH3CN converting to CH3CH2NH2, option C shows CH3CH2Cl converting to CH3CH2NH2, and option D shows CH3COCH3 converting to CH3CHOHCH3. An answer box is provided at the bottom with a 1-mark allocation on the right.
Question text

9 Which reaction is not a reduction?

A C6H5NO2 C6H5NH2

B CH3CN CH3CH2NH2

C CH3CH2Cl CH3CH2NH2

D CH3COCH3 CH3CHOHCH3

Your answer

[1]

Mark scheme

Show the mark scheme The mark scheme indicates that the correct answer for question 9 is C, worth 1 mark under AO1.2.

9 C 1 AO1.2

How to answer it

Identifying Reduction Reactions in Organic Synthesis

What this question tests

This question assesses your ability to recognise reduction reactions within organic chemistry contexts (specifically functional group interconversions involving nitro compounds, nitriles, halogenoalkanes, and carbonyls), and distinguish them from nucleophilic substitution mechanisms.

Question 9

Exam Breakdown & Analysis

✅ Correct Answer: C

Reaction C ( CH₃CH₂Cl → CH₃CH₂NH₂ ) is not a reduction. It is a nucleophilic substitution reaction where ammonia reacts with a haloalkane.

💡 Key Knowledge

  • Reduction in organic chemistry often corresponds to a decrease in oxygen content, an increase in hydrogen content, or acceptance of electrons (e.g., adding H or forming amines from nitro groups/nitriles).
  • Option A: Reduction of nitrobenzene to phenylamine ( C₆H₅NO₂ → C₆H₅NH₂ ) using Sn / HCl.
  • Option B: Reduction of a nitrile to a primary amine ( CH₃CN → CH₃CH₂NH₂ ) using LiAlH₄ or H₂ / Ni.
  • Option D: Reduction of a ketone to a secondary alcohol ( CH₃COCH₃ → CH₃CHOHCH₃ ) using NaBH₄.

🧠 Exam Technique

Scan through the options and identify the functional group transformation taking place in each. Look at the starting material vs. the product. If a halogen is being replaced by an amine group without changing oxidation states or adding hydrogen across multiple bonds, suspect substitution rather than reduction.

❌ Common Errors

Students often incorrectly assume that any reaction producing an amine must be a reduction. While reducing nitriles and nitro compounds yields amines, forming an amine via haloalkanes involves replacing a halogen atom via nucleophilic substitution.

Mark Scheme Allocation: 1 mark available for identifying option C (AO1.2 - Demonstrating knowledge and understanding of organic chemistry reactions).

Topics

Module 6: Organic chemistry and analysis · 6.2 Nitrogen compounds, polymers and synthesis · 6.1 Aromatic compounds, carbonyls and acids

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.