How to deduce the polymerisation reaction for any alkene

4 marks · Normal

A new polymer, poly(2-chloropropene), is formed from the alkene 2-chloropropene (CH2=CClCH3).

(a)

Draw the displayed formula of the monomer, 2-chloropropene.

[1 mark]

(b)

Show the displayed formula of the repeat unit of poly(2-chloropropene). Indicate continuation bonds at both ends.

[2 marks]

(c)

State the type of polymerisation that occurs.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) Displayed structure showing all atoms and bonds of CH2=CClCH3 (C=C with one carbon attached to H2, the other to Cl and CH3)

(b) Displayed repeat unit of poly(2-chloropropene) with two carbons in backbone, Cl and CH3 groups, and continuation bonds at each end

Must show: Correct skeletal structures for a, b, Continuation bonds for the repeat unit

Also accept: Correctly drawn structural or displayed formulae with correct bonding

Common mistakes: Structures with missing/incorrect bonds; Omitting continuation bonds

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Correctly drawn displayed formula for 2-chloropropene, showing clearly the C=C, H, Cl, and CH3 groups attached appropriately.

M1 (b) · 1 mark · Opens double bond and forms backbone for repeat unit, showing correct arrangement for poly(2-chloropropene).

A1 (b) · 1 mark · Shows the continuation bonds at each end of the repeat unit.

B2 (c) · 1 mark · States that the polymerisation type is addition polymerisation.

Worked solution

a) The displayed formula for 2-chloropropene is:

b) The displayed formula for the repeat unit is:

Continuation bonds should be shown at each end.

c) The reaction is an addition polymerisation.