Addition Polymers from Alkenes

Key Concepts

• Alkenes: Molecules with a carbon-carbon double bond (unsaturated).
  • Example: Ethene
• Polymerization: Process where alkenes can form long chains (polymers) by breaking the double bond under the right conditions.

Monomers and Polymers

• Monomer: The repeating unit in polymers.
• Polymerization Reaction Representation:
  • Traditional representation uses multiple monomers on the left and the polymer on the right.
  • Improved representation shows a single monomer on the left and the repeating unit on the right.
  • Repeating unit consists of the same atoms as the monomer (e.g., 2 carbons, 4 hydrogens).

Drawing Polymers

• Bond Orientation:
  • Draw bonds of the monomer facing up and down.
  • Draw empty bonds of the repeating unit pointing out to the left and right.
• End Notation:
  • Use "n" to indicate the number of repeating units.
  • Example: If n = 10, then there are 10 ethene molecules and the polymer has 10 repeating units.

Example: Addition Polymerization of Butene

1. Identify Double Bond: Locate between the first two carbons.
2. Arrange Groups:

• Redraw atoms as separate groups.
• Place groups above and below the double-bonded carbons.

3. Simplify Groups:

• For larger groups, count carbons and hydrogens to write in shorthand (e.g., C2H5).

4. Draw Reaction:

• Include brackets and "n" in front for the number of repeating units.
• Draw the reaction arrow to indicate the process.

Naming Polymers

• To name the polymer, use the prefix "poly" followed by the monomer's name in brackets.
  • Example:
    • Butane ➔ Polybutane
    • Ethylene ➔ Polyethylene
    • Chloroethene ➔ Polychloroethylene

Reaction Conditions

• Addition polymerization requires high pressure and a catalyst.
  • These may be noted on the reaction arrow but are not mandatory to include.

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Conclusion

• Understanding these concepts and techniques is crucial for working with addition polymers from alkenes.