Chapter summary
Polymers and Organic Chemistry, at a glance
Read organic structures, predict reactions and explain why a protein or plastic behaves as it does.
A-Level 8873, revised syllabus (2026-2027)
Quick revision
Revisit the essentials, then return to an explanation when you need it.
| Term | Definition to write |
|---|---|
| Homologous series | A family of compounds with the same general formula and functional group, similar chemical properties, and a gradual change in physical properties as the molecules get larger. Successive members differ by CH2. |
| Structural (constitutional) isomers | Compounds with the same molecular formula but different structural formulae. |
| Polymer | A macromolecule built up from many monomers, with an average relative molecular mass of at least 1000 or at least 100 repeat units. |
| Addition polymerisation | Monomers containing C=C bonds join together to form a polymer, with no other product formed. |
| Condensation polymerisation | Monomers with two functional groups join together to form a polymer, with a small molecule such as water lost at each link. |
| Thermoplastic | A polymer of linear chains held by intermolecular forces. It softens on heating, can be remoulded and recycled. |
| Thermosetting polymer | A polymer with covalent cross-links between chains. It does not soften on heating (it decomposes), so it cannot be remoulded; it is rigid. |
- Locate the group
Mark C=C, C-X, OH, C=O, COOH, COO or CONH.
- Read the conditions
Aqueous vs ethanolic NaOH, oxidant vs reductant, and acid vs alkali hydrolysis change the answer.
- Preserve the skeleton
Change only the reacting bonds; include small products, charge and counter-ions as needed.
- Check the result
Conserve atoms and charge, then name the new functional group and product.
| Pair | Deciding point |
|---|---|
| Constitutional / cis-trans | Different connections / same connections with restricted C=C arrangement. |
| Ester / amide | Carbonyl C attached to O / N. Acid + amine requires DCC for the specified amide route, not simple acid-base mixing. |
| Acid / alkali hydrolysis | Acid medium retains COOH and protonates amines; alkali gives COO- and unprotonated amine/ammonia products. |
| Denaturation / hydrolysis | Loss of the specific fold / cleavage of covalent peptide links. |
| Thermoplastic / thermoset | Separate chains can move on warming / covalent crosslinks prevent ordinary remelting. |
Named materials: LDPE branches pack less closely than HDPE. Nylon 6,6 can form more hydrogen bonds between chains than PET. PVA OH groups bond with water, while PVC resists water. PP resists the ester hydrolysis that can damage PET in strong alkali.
Poly(alkenes) are unreactive, so they biodegrade with difficulty. Ester and amide links can be hydrolysed, but real rates depend on conditions. Recycling decisions must weigh economic, environmental and social effects, not only how much is recovered.
Quick recall
What are structural (constitutional) isomers?