20.1.2—Repeat units of addition polymers
- Syllabus
- 9701–2028–2029
- Objective
- 20.1.2
- Level
- AS
Recover an addition-polymer repeat unit by reopening the monomer double bond
In an addition polymer, the alkene C=C becomes a C–C link in the backbone. The repeat unit is the monomer with the double bond opened and free valencies shown at both ends.
Put the repeat unit in brackets with n. Keep substituents attached to the same carbon positions as in the monomer and do not add a small molecule.
CH₂=CHCl gives [–CH₂–CHCl–]ₙ, poly(chloroethene). CH₂=CHCH₃ gives [–CH₂–CH(CH₃)–]ₙ.
Do not leave C=C inside the repeat unit or move a substituent to the wrong backbone carbon.
ConceptA-Level CAIE Chemistry AS