AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Condensation polymers are formed by reactions between: dicarboxylic acids…
Full specification wording
Condensation polymers (A-level only): Condensation polymers are formed by reactions between: dicarboxylic acids and diols dicarboxylic acids and diamines amino acids.
In a condensation polymerisation each new link is made by a reaction that also throws out a small molecule, usually water, or hydrogen chloride if a diacyl dichloride is used instead of the diacid.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 1 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
In a condensation polymerisation each new link is made by a reaction that also throws out a small molecule, usually water, or hydrogen chloride if a diacyl dichloride is used instead of the diacid. For a chain to grow at both ends, every monomer needs two reacting groups. A diol and a dicarboxylic acid give an ester link, -COO-, repeated all the way along, so the product is a polyester. A diamine and a dicarboxylic acid give an amide link, -CONH-, so the product is a polyamide. An amino acid needs no partner, because it carries an -NH₂ at one end and a -COOH at the other, so it condenses with itself over and over to give a polyamide, which is what a polypeptide is.
What earns the marks
- Water, or hydrogen chloride from a diacyl dichloride, named as the small molecule lost.
- Each monomer needing two functional groups so the chain can grow at both ends.
- The ester link formed from a diol and a dicarboxylic acid.
- The amide link formed from a diamine and a dicarboxylic acid, or from an amino acid alone.
Common mistakes and how to put them right
Using a monomer with only one functional group, which caps the chain instead of extending it.
Calling the product of two C=C monomers a condensation polymer.
Leaving the water molecules out of the equation for the polymerisation.
Calling the amide link an ester because it contains a C=O group.
Exam tips
- Count the functional groups on every monomer first. Two groups means condensation is possible; one means it is not.
- For each link you draw, cross out an -OH and an -H and write the water molecule you removed.
Try the lesson
The start of the Condensation polymers (A-level only): Condensation polymers are formed by reactions between: dicarboxylic acids and diols dicarboxylic acids and diamines amino acids. lesson, made from checked teaching notes for this specification point.
Have a go first
Which pair of monomers reacts together to form a polyester by condensation polymerisation?
Listen
In a condensation polymerisation each new link is made by a reaction that also throws out a small molecule, usually water, or hydrogen chloride if a diacyl dichloride is used instead of the diacid. For a chain to grow at both ends, every monomer needs two reacting groups. A diol and a dicarboxylic acid give an ester link, -COO-, repeated all the way along, so the product is a polyester. A diamine and a dicarboxylic acid give an amide link, -CONH-, so the product is a polyamide. An amino acid needs no partner, because it carries an -NH₂ at one end and a -COOH at the other, so it condenses with itself over and over to give a polyamide, which is what a polypeptide is. A strong answer earns marks for these points. water, or hydrogen chloride from a diacyl dichloride, named as the small molecule lost. each monomer needing two functional groups so the chain can grow at both ends. the ester link formed from a diol and a dicarboxylic acid. the amide link formed from a diamine and a dicarboxylic acid, or from an amino acid alone. Exam tip: Count the functional groups on every monomer first. Two groups means condensation is possible; one means it is not.
Key words
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condensation polymerisation
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difunctional monomers
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ester and amide links
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amino acid self-condensation
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See every definition
- condensation polymerisation
- A reaction in which each new link is made by a reaction that also throws out a small molecule, usually water, or hydrogen chloride if a diacyl dichloride is used.
- difunctional monomers
- Every monomer needs two reacting groups so that the chain can grow at both ends.
- ester and amide links
- A diol and a dicarboxylic acid give an ester link, -COO-, while a diamine and a dicarboxylic acid give an amide link, -CONH-.
- amino acid self-condensation
- An amino acid carries an -NH₂ at one end and a -COOH at the other, so it condenses with itself over and over to give a polyamide.
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