How to deduce the polymerisation reaction for any alkene
3 marks · NormalPoly(bromopropene) is made by the addition polymerisation of the monomer CH2=CHCH2Br.
Explain how you could deduce the structure of the monomer from the structure of the polymer poly(bromopropene).
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One way to deduce the monomer is to identify the repeating unit in the polymer, add a double bond between the two central carbon atoms of the repeat unit, and remove the continuation bonds to restore the original monomer structure.
Must show: Describes identifying the repeat unit, Mentions restoring double bond, Mentions removal of continuation bonds
Also accept: Suitable equivalent procedural description
Common mistakes: Failing to mention double bond restoration; Describing addition instead of deduction
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Marking points
M1 · 1 mark · Recognises that the repeat unit gives the monomer's arrangement of atoms/groups.
M2 · 1 mark · States that restoring the double bond between carbons is needed to form the monomer.
A1 · 1 mark · Appropriately describes removing continuation bonds (ends) to form the discrete monomer.
Worked solution
To deduce the monomer from a polymer:
1. Identify the repeat unit within the polymer structure.
2. Restore a double bond between the two central carbons in the repeat unit backbone.
3. Remove the continuation bonds at each end to produce the monomer molecule.