AQA A-Level Chemistry Paper 3, June 2022: Question 27

1 mark · Easy difficulty · Multiple Choice

Identify which compound can react with suberoyl chloride to form a polymer.

Practise this question

Question

Question 27 asks: Suberoyl chloride, ClOC(CH2)6COCl, is commonly used in the manufacture of polymers. Which compound can form a polymer with suberoyl chloride? Four multiple choice options are given: A H2NCH2CH2NH2, B ClOCCH2COCl, C CH3CH2CONH2, and D HOOCCH2COOH, each followed by an answer box.
Question text

27 Suberoyl chloride, ClOC(CH2)6COCl, is commonly used in the manufacture of

polymers.

Which compound can form a polymer with suberoyl chloride?

[1 mark]

A H2NCH2CH2NH2

B ClOCCH2COCl

C CH3CH2CONH2

D HOOCCH2COOH

Mark scheme

Show the mark scheme Mark scheme table row for question 27 shows: correct answer 'A (AO2)', 1 mark, with the structure 'H2NCH2CH2NH2'.

27 A (AO2) 1 H2NCH2CH2NH2

How to answer it

Condensation Polymerisation: Diacyl Chlorides & Polyamides

📋 What this question tests

This question assesses your understanding of condensation polymerisation and the reactivity of acyl chlorides:

  • Identifying bifunctional monomers required for polymer chain growth.
  • Recognising the reaction between acyl chlorides ( -COCl ) and primary amines ( -NH₂ ) to form amide linkages.
  • Eliminating non-reactive or monofunctional options that cannot sustain polymerisation.
Question 27 • Multiple Choice [1 Mark]

Identifying Monomers for Polymer Formation

Suberoyl chloride, ClOC(CH₂)₆COCl, reacting to form a polymer

✅ Correct Answer

A: H₂NCH₂CH₂NH₂ (ethane-1,2-diamine)

Mark Scheme Breakdown:
1 mark for selecting option A.

Suberoyl chloride is a diacyl chloride containing two electrophilic -COCl groups. To build a polymer chain, it must react with a molecule possessing two nucleophilic functional groups. Ethane-1,2-diamine has two -NH₂ groups, which react via nucleophilic addition-elimination to form a continuous polyamide with the loss of HCl .

💡 Key Knowledge

  • Diacyl chloride + Diamine → Polyamide + 2n HCl
  • Requirement for Polymerisation: Both participating monomers must be at least difunctional (have two reactive ends). If a monomer only has one reactive end, it terminates the chain.
  • Condensation vs Addition: Condensation polymers release a small byproduct molecule (here, HCl ) during every bond-forming step.
  • Repeating Unit Formed:
    -[CO-(CH₂)₆-CO-NH-CH₂CH₂-NH]ₙ-

🧠 Exam Technique: Systematic Elimination

Scan the functional groups of every distractor to check for complementary reactivity and bifunctionality:

  • A: H₂NCH₂CH₂NH₂: Difunctional nucleophile (two -NH₂ groups). Reacts vigorously with acyl chlorides → Forms polyamide.
  • B: ClOCCH₂COCl: Diacyl chloride. Two electrophilic groups cannot react with each other → No reaction.
  • C: CH₃CH₂CONH₂: Primary amide with only one reactive end (monofunctional). Would cap the acyl chloride without propagating a chain → No polymer.
  • D: HOOCCH₂COOH: Dicarboxylic acid. Both carboxylic acids and acyl chlorides are acylating agents (electrophiles); they do not condense together → No polymer.

❌ Common Errors & Misconceptions

  • Confusing an Amide with an Amine (Option C): Seeing the -NH₂ in CH₃CH₂CONH₂ and assuming it can form a polyamide. Amides are poor nucleophiles and this molecule is only monofunctional.
  • Mismatching Electrophiles (Option D): Remembering that dicarboxylic acids make polymers (e.g. Terylene, Nylon 6,6) and blindly choosing Option D, forgetting that an acid reacts with an amine or alcohol, not an acyl chloride.
  • Forgetting Byproduct Identity: Unlike dicarboxylic acids which release H₂O , diacyl chlorides release misty fumes of acidic HCl gas.

Topics

Organic Chemistry · 3.3.9 Carboxylic Acids and Derivatives · 3.3.12 Polymers

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.