AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
For example: ethanediol and hexanedioic acid polymerise to produce a…
Full specification wording
Condensation polymerisation (HT only): For example: ethanediol and hexanedioic acid polymerise to produce a polyester: Students should be able to explain the basic principles of condensation polymerisation by reference to the functional groups in the monomers and the repeating units in the polymers.
Ethanediol, HO–CH₂–CH₂–OH, has two alcohol groups.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 4 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Ethanediol, HO–CH₂–CH₂–OH, has two alcohol groups. Hexanedioic acid, HOOC–(CH₂)₄–COOH, has two carboxylic acid groups. When they react, an alcohol group on ethanediol reacts with a carboxylic acid group on hexanedioic acid to form an ester link, releasing water. Because both monomers have two functional groups, the process repeats and builds a polyester chain. The repeating unit shows the two monomer residues joined by ester links, with the atoms of the eliminated water molecules missing. To explain the principles, identify the functional groups in each monomer, state the link formed, and show how the repeating unit reflects the loss of water at each join.
What earns the marks
- Ethanediol contains two alcohol groups and hexanedioic acid contains two carboxylic acid groups.
- An alcohol group reacts with a carboxylic acid group to form an ester link.
- Water is eliminated at each ester link formed.
- The repeating unit shows both monomer residues joined by ester links.
- The repeating unit contains fewer atoms than the monomers because water has been lost.
- The two functional groups on each monomer allow the chain to continue growing.
Common mistakes and how to put them right
Drawing the repeating unit with the water molecule still present.
Put it right by removing the atoms of water at each ester link.
Showing only one functional group reacting.
Put it right by showing both ends of each monomer able to react.
Labelling the link as an amide link.
Put it right by naming it an ester link when alcohol and carboxylic acid groups react.
Exam tips
- Identify the functional groups in each monomer before drawing the repeating unit.
- Show the ester link clearly and account for the eliminated water.
- Use the monomer structures to check that the repeating unit has the correct number of carbon atoms.
Try the lesson
The start of the Condensation polymerisation (HT only): For example: ethanediol and hexanedioic acid polymerise to produce a polyester: Students should be able to explain the basic principles of condensation polymerisation by reference to the functional groups in the monomers and the repeating units in the polymers. lesson, made from checked teaching notes for this specification point.
Have a go first
Ethanediol and hexanedioic acid react together in a condensation polymerisation. Which functional groups do these two monomers contain?
Listen
Ethanediol, HO–CH₂–CH₂–OH, has two alcohol groups. Hexanedioic acid, HOOC–(CH₂)₄–COOH, has two carboxylic acid groups. When they react, an alcohol group on ethanediol reacts with a carboxylic acid group on hexanedioic acid to form an ester link, releasing water. Because both monomers have two functional groups, the process repeats and builds a polyester chain. The repeating unit shows the two monomer residues joined by ester links, with the atoms of the eliminated water molecules missing. To explain the principles, identify the functional groups in each monomer, state the link formed, and show how the repeating unit reflects the loss of water at each join. A strong answer earns marks for these points. Ethanediol contains two alcohol groups and hexanedioic acid contains two carboxylic acid groups. An alcohol group reacts with a carboxylic acid group to form an ester link. Water is eliminated at each ester link formed. The repeating unit shows both monomer residues joined by ester links. A common slip: Drawing the repeating unit with the water molecule still present. Instead, removing the atoms of water at each ester link. Exam tip: Identify the functional groups in each monomer before drawing the repeating unit.
See it
Key words
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Ester links
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Functional groups
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Repeating units
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Condensation polymerisation
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See every definition
- Ester links
- The link formed when an alcohol group reacts with a carboxylic acid group, with water eliminated at each link formed.
- Functional groups
- The groups in the monomers, such as the alcohol groups and carboxylic acid groups, whose reaction allows the chain to continue growing.
- Repeating units
- The part of the polymer showing both monomer residues joined by ester links, with the atoms of the eliminated water molecules missing.
- Condensation polymerisation
- The process in which monomers react so that water is eliminated at each ester link formed and a polyester chain is built.
Label the diagram
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1Box 1
2Box 2
3Box 3
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