Synthetic Polymers
5 marks · EasyPoly(pent-1-ene) is a synthetic addition polymer made from the monomer pent-1-ene.
Draw the displayed formula of the repeat unit of poly(pent-1-ene).
State the name and displayed formula of the monomer used to make poly(pent-1-ene).
Give the type of polymerisation occurring and briefly explain what happens to the double bond in the monomer during the reaction.
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 formula: H H H H | | | | ---C—C—C—C—C--- ( [—CH₂—CH(CH₂CH₃)—] ) | | | H chains H chains (continuation bonds left and right) · must show Correct number of carbon atoms (5), Continuation bonds on each end of repeat unit, All hydrogens correctly shown consistent with polymer structure
(b) Name: pent-1-ene Displayed formula: CH₂=CH–CH₂–CH₂–CH₃ · must show Correct name: pent-1-ene, Displayed formula with C=C between carbons 1 and 2
(c) Type: Addition polymerisation. The double bond in the monomer opens up to form single bonds, so the carbon atoms link together in a long chain and no other product is formed. · must show States: addition polymerisation, Double bond opens/connects units, No other product formed
Common mistakes: Drawing too few or too many carbon atoms in the repeat unit; Omitting the continuation bonds on the repeat unit; Giving a saturated monomer; Naming the reaction incorrectly (e.g. condensation polymerisation)
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Draws a repeat unit of poly(pent-1-ene) with correct carbon backbone (5 carbons), showing displayed formula.
A1 (a) · 1 mark · Shows correct continuation bonds at each end and correct number of hydrogen atoms for the repeat unit.
B1 (b) · 1 mark · States the correct monomer name: pent-1-ene.
B2 (b) · 1 mark · Draws correct displayed formula for pent-1-ene (CH₂=CH–CH₂–CH₂–CH₃).
B3 (c) · 1 mark · States the correct type of polymerisation and explains that the double bond opens to allow monomers to join, with no other product.
Worked solution
a) The repeat unit of poly(pent-1-ene):
One way to draw this is as follows (brackets and continuation bonds):
A full displayed formula (vertical layout):
H H H H H | | | | | --C--C--C--C--C-- | | | | | H CH2CH2CH3 H H Continuation bonds on the left and right through brackets.
b) Name: pent-1-ene Displayed formula: CH₂=CH–CH₂–CH₂–CH₃ (double bond between C1 and C2).
c) This is addition polymerisation. The double bond in the pent-1-ene monomer opens so that each carbon atom forms new single bonds with neighbouring units, creating a long chain. No other products are formed during the process.