OCR A-Level Chemistry Synthesis and analytical techniques (02), June 2023: Question 12

1 mark · Medium difficulty · Multiple Choice

Identify which compound reacts with ethanoyl chloride from a given list of four options.

Practise this question

Question

Multiple-choice question 12 asking 'Which compound reacts with ethanoyl chloride?'. Four options A, B, C, and D show chemical structures: A is methyl propanoate, B is butan-2-one (or similar ketone structure), C is 1-chlorobutan-2-one, and D is 1-aminobutan-2-one containing an amine group that can react with acyl chlorides. An empty answer box is provided below.
Question text

12 Which compound reacts with ethanoyl chloride?

O

A

O

B

O

Cl

C

O

D NH2

O

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer for question 12 is D, worth 1 mark, assessed under AO1.2.

12 D 1 AO1.2

How to answer it

Reactivity of Acyl Chlorides

What this question tests

This question assesses your knowledge of organic functional groups and their nucleophilic addition-elimination reactions. Specifically, it tests your understanding of how acyl chlorides (like ethanoyl chloride) react with compounds containing active lone pairs on nitrogen or oxygen, such as primary amines, alcohols, and water, compared to unreactive functional groups like ketones or haloalkanes under standard conditions.

Question 12

Exam Breakdown & Solution

✅ Correct Answer: D

Compound D is an amine (specifically containing a -CH₂NH₂ group). Amines act as strong nucleophiles due to the lone pair of electrons on the nitrogen atom, allowing them to readily attack the delta-positive carbonyl carbon of ethanoyl chloride to form an N-substituted amide.

💡 Key Knowledge

  • Acyl chlorides are extremely reactive carboxylic acid derivatives due to the strong electron-withdrawing chlorine and carbonyl oxygen atoms making the carbonyl carbon highly electrophilic (delta positive).
  • They react via nucleophilic addition-elimination with compounds possessing a labile H attached to an electronegative atom with a lone pair (e.g., -OH , -NH₂ ).

🧠 Exam Technique

Scan through the options and identify the functional group in each:

  • A: Ester ( -COOCH₃ ) - no active nucleophile.
  • B: Ketone ( -COCH₃ ) - does not react with acyl chlorides.
  • C: Haloalkane/Ketone combination - aliphatic chlorine is resistant to substitution under these conditions compared to acyl chlorides.
  • D: Primary amine ( -CH₂NH₂ ) - reacts vigorously.

❌ Common Errors

Students frequently confuse ketones (like structure B) with compounds that can undergo nucleophilic attack. Remember that ketones are electrophilic themselves, not nucleophiles, and do not possess a labile hydrogen or lone pair ready to substitute into an acyl chloride system.

Mark Scheme Allocation: 1 mark awarded for selecting D (AO1.2 - Demonstrating knowledge and understanding of organic chemistry reactions).

Topics

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

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.