Learning focus
Develop accurate organic nomenclature, connect functional groups to reactions, draw structural and polymer formulae, interpret industrial processes and apply evidence to unfamiliar compounds.
Polyester formation
A dicarboxylic acid reacts with a diol. Each -COOH/-OH pair forms an ester link, -COO-, and water. Repetition at both ends produces a long chain.
Deducing structures
In a polymer, locate -COO- links. Cutting each ester linkage conceptually and restoring OH to both appropriate ends reveals the dicarboxylic acid and diol monomers.
PET
PET is a required polyester structure. Its full name is not required. Learners must identify the ester link and relate the alternating residues to a diacid and a diol.
Chemical recycling
PET can be converted back into monomers and re-polymerised. This can preserve material value, though collection, sorting, contamination and energy use remain practical considerations.
High-value recall and connections
Essential recall: Which linkage identifies a polyester? -COO-. Which monomer types form it? A dicarboxylic acid and a diol. What can happen to PET during chemical recycling? It can be converted to monomers and re-polymerised. Practical connection: Mark ester links in a PET repeat structure and use coloured brackets to identify the two monomer residues. Examination connection: The ester link is -COO-, not simply C-O.
Practical or data skill
Mark ester links in a PET repeat structure and use coloured brackets to identify the two monomer residues.
Examination tip
The ester link is -COO-, not simply C-O.
Review questions and suggested answers
Question 1
Which linkage identifies a polyester?
Suggested answer
-COO-.
Question 2
Which monomer types form it?
Suggested answer
A dicarboxylic acid and a diol.
Question 3
What can happen to PET during chemical recycling?
Suggested answer
It can be converted to monomers and re-polymerised.
