A research chemist is investigating the production of nylon-6,6, a polyamide used in the manufacture of ropes and parachutes. Explain how nylon-6,6 is formed by condensation polymerisation, including the role of the functional groups on the monomers and the small molecule produced during the reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Nylon-6,6 is a polyamide synthesised from two monomers: a diamine and a dicarboxylic acid. Each monomer contains two functional groups. The polymer chains are long and strong, making nylon suitable for high-tension applications such as climbing ropes.
Model answer (5 marks)
Nylon‑6,6 is produced by a condensation polymerisation in which the two monomers, hexamethylenediamine and adipic acid, each possess two functional groups. The –NH₂ groups of the diamine react with the –COOH groups of the dicarboxylic acid to give an amide linkage (–CO–NH–) and release a small molecule.
1. The reaction is a condensation polymerisation – monomers join while a small molecule is lost.
2. The small molecule released is water.
3. Each monomer is bifunctional, allowing the chain to grow in both directions.
4. The –NH₂ reacts with –COOH to form the –CO–NH– amide bond (a peptide bond).
5. Repetition of this step many times gives a long nylon‑6,6 polymer chain.
1. The reaction is a condensation polymerisation – monomers join while a small molecule is lost.
2. The small molecule released is water.
3. Each monomer is bifunctional, allowing the chain to grow in both directions.
4. The –NH₂ reacts with –COOH to form the –CO–NH– amide bond (a peptide bond).
5. Repetition of this step many times gives a long nylon‑6,6 polymer chain.
Examiner tips
- Use the term "condensation polymerisation" and mention water as the by‑product.
- Show the bifunctional nature of the monomers and the amide linkage formed.
- Explain that the reaction repeats to give a long chain.
Mark scheme (5 marks)
- Condensation polymerisation involves monomers joining together and losing (releasing) small molecules
- The small molecule released is water
- Each monomer must have two functional groups (bifunctional) so that the chain can grow in both directions / polymerisation can continue
- The amine functional group (–NH2) reacts with the carboxylic acid functional group (–COOH) to form an amide (–CO–NH–) linkage / peptide bond
- The process repeats many times to produce a long polymer chain
Key terms in this question
condensation polymerisation · monomers · functional groups · polymer
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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