OCR A-Level Chemistry Synthesis and analytical techniques (02), June 2024: Question 12

1 mark · Easy difficulty · Multiple Choice

Identify the other product formed when 1,6-diaminohexane reacts with hexanedioyl dichloride to form a polyamide.

Practise this question

Question

Multiple choice question 12 asks about the reaction between 1,6-diaminohexane (H2N(CH2)6NH2) and hexanedioyl dichloride (ClOC(CH2)4COCl) to form a polyamide and one other product. Four options are given: A, HCl; B, H2O; C, CO; D, NH3. A box for the student's answer is shown at the bottom.
Question text

12 1,6-Diaminohexane, H2N(CH2)6NH2, reacts with hexanedioyl dichloride, ClOC(CH2)4COCl to

form a polyamide and one other product.

What is the other product formed in this reaction?

A HCl

B H2O

C CO

D NH3

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme for question 12 indicating the correct answer is A, worth 1 mark, allowing HCl.

12 A 1 ALLOW HCl

How to answer it

Polyamide Condensation Polymerisation

What this question tests

This question assesses your understanding of condensation polymerisation reactions—specifically the reaction between a diamine and an acyl chloride to form a polyamide. It tests your ability to identify small molecules eliminated during the formation of amide linkages.

Question 12

By-product of Polyamide Synthesis

Identifying the small molecule eliminated during condensation polymerisation

✅ Correct Answer: A (HCl)

The reaction between an amine ( H₂N(CH₂)₆NH₂ ) and an acyl chloride ( ClOC(CH₂)₄COCl ) proceeds via nucleophilic addition-elimination. The hydrogen from the amine group combines with the chlorine atom from the acyl chloride functional group to eliminate hydrogen chloride ( HCl ).

Marks: 1 / 1. Accept HCl or HCℓ .

💡 Key Knowledge

  • Condensation Polymerisation: Involves monomers with two functional groups reacting to form a polymer chain accompanied by the elimination of a small molecule (like H₂O or HCl ).
  • Acyl Chlorides vs Carboxylic Acids: When dicarboxylic acids react with diamines, water ( H₂O ) is eliminated. When acyl chlorides are used instead, hydrogen chloride ( HCl ) is eliminated because acyl chlorides are much more reactive.

🧠 Exam Technique

Look carefully at the functional groups given in the stem: -NH₂ and -COCl . Whenever you spot an acyl chloride reacting with an amine or an alcohol, think HCl elimination instantly!

❌ Common Errors

  • Choosing B (H₂O): A very common student mistake is assuming all condensation polymers eliminate water (like polyesters formed from diols and dicarboxylic acids, or proteins). Always check if an acyl chloride is present!
  • Confusing reagents: Guessing NH₃ or CO due to misremembering nitrogen-containing breakdown products.

Topics

Module 6: Organic chemistry and analysis · 6.2 Nitrogen compounds, polymers and synthesis

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.