2.4.4 Addition Polymers
Converting alkenes into long chain macromolecules.
Key Definitions
Monomer: Small reactive molecule containing a C=C double bond (Alkene).
Polymer: Long chain macromolecule formed from many monomers.
Repeating Unit: The specific arrangement of atoms that repeats 'n' times.
Mechanism Details
Process: The -bond of the alkene breaks, allowing carbons to form new -bonds with neighbors.
Atom Economy: 100%. All atoms in the monomer end up in the polymer. No waste.
Examiner Strategy: Drawing Repeating Units
The most common mistake is failing to draw the "continuation bonds". Follow these steps:
- Flatten the Monomer: Draw the C=C bond flat horizontally. Push any attached groups (like or ) strictly up or down.
- Break the Bond: Turn the double bond (=) into a single bond (-).
- Extend: Draw new single bonds extending outwards horizontally from each carbon.
- Bracket: Draw square brackets that cut through these extension bonds. Add the subscript 'n'.
Propene (Monomer)
Polypropene (Polymer)