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*Revision Materials and Past Papers* 2.1.1 Atomic structure and isotopes 2.1.2 Compounds, formulae and equations 2.1.3 Amount of substance 2.1.4 Acids 2.1.5 Redox 2.2.1 Electron structure 2.2.2 Bonding and structure 3.1.1 Periodicity 3.1.2 Group 2 3.1.3 The halogens 3.1.4 Qualitative analysis 3.2.1 Enthalpy 3.2.2 Reaction Rates 3.2.3 Chemical equilibrium 4.1 Basic concepts and hydrocarbons 4.1.2 Alkanes 4.1.3 Alkenes 4.2.1 Alcohols 4.2.2 Haloalkanes 4.2.3 Organic synthesis 4.2.4 Analytical techniques 5.1.1 How fast? 5.1.2 How far? 5.1.3 Acids, bases and buffers 5.2.1 Lattice enthalpy 5.2.2 Enthalpy and entropy 5.2.3 Redox and electrode potentials 5.3.1 Transition elements 5.3.2 Qualitative analysis 6.1.1 Aromatic compounds 6.1.2 Carbonyl compounds 6.1.3 Carboxylic acids and esters 6.2.1 Amines 6.2.2 Amino acids, amides and chirality 6.2.3 Polyesters and polyamides 6.2.4 Carbon–carbon bond formation 6.2.5 Organic synthesis 6.3.1 Chromatography and qualitative analysis 6.3.2 Spectroscopy Required Practicals

4.1.3 Alkenes

Addition reactions of alkenesPolymers from alkenesProperties of alkenesStereoisomerism in alkenes

Addition Polymers

Specification Reference 4.1.3 (j)–(l)

Quick Notes:

  • Alkenes form polymers via addition polymerisation
    • Waste polymer processing benefits:
    • Incineration (Combustion) for energy
      (requires safe removal of toxic gases like HCl from PVC)
    • Organic feedstock for new plastics

Full Notes:

Alkenes undergo addition polymerisation to form long-chain molecules called addition polymers. Each monomer must contain a C=C bond.

Example ethene → poly(ethene)

OCR (A) A-Level Chemistry polymerisation diagram showing ethene forming poly(ethene) via addition polymerisation.

Drawing Polymer Structures

An addition polymer’s repeating unit is based on the monomer structure.

It is possible to draw a repeating unit and polymer from a monomer:

OCR (A) A-Level Chemistry steps showing how to draw the repeating unit of poly(chloroethene) from chloroethene.
  1. Redraw the monomer with the C=C double bond in the middle of the structure.
  2. Break the C=C double bond.
  3. Extend single bonds from the two carbons to show the continuation of the polymer chain.

To find the monomer from a polymer chain:

OCR (A) A-Level Chemistry diagram showing how to identify the monomer from a polymer repeating unit by restoring the C=C bond.
  1. Identify the repeating unit.
  2. Restore the C=C double bond.

Disposal and Sustainability of Polymers

Polymers are not biodegradable and cause environmental issues. Chemists have developed ways to reduce impact:

Concerns with incineration include toxic gases (e.g. HCl from PVC). These can be neutralised by chemical scrubbers.