Importance of Functional Groups in the Synthesis of Polymers

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Importance of Functional Groups in the Synthesis
of Polymers

• Indicators C-3.5 and C-3.7
• South Carolina Science Standards
• Chemistry Section

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Nylon SynthesisExample of a step reaction
The reaction illustrated here has been simplified
and is just one of many methods for synthesizing
nylon. The actual reaction has many more steps.
sebacoyl dichloride (decanedioyl dichloride) This
is the same thing as 1,10-dichloro-1,10-decan-1,10
-dial for which you wrote a structural formula in
the prelab quiz
carbonyl group
alkyl halide group (chloro- group)
amine group
Pay close attention to how the reaction takes
place between the functional groups. In this
case the reaction occurs between an amine group
and a carbonyl group.
1,6-hexandiamine This is the same thing
as hexane-1,6-diamine for which you wrote a
structural formula in the prelab quiz
An alkyl halide group (a chloro- group) is also
attached to the same carbon that is part of the
carbonyl group.
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Notice also that the reaction is NOT taking place
between the hydrocarbon groups in the parent
chains or between the hydrocarbon groups and
functional groups.
sebacoyl dichloride (decanedioyl dichloride) This
is the same thing as the 1,10-dichloro-1,10-dideca
nal for which you wrote a structural formula in
the prelab quiz
hydrocarbon parent chain
hydrocarbon parent chain
1,6-hexandiamine This is the same thing
as Hexane-1,6-diamine for which you wrote a
structural formula in the prelab quiz
The reaction IS taking place between functional
groups.
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sebacoyl dichloride (decanedioyl dichloride) This
is the same thing as the 1,10-dichloro-1,10-dideca
nal for which you wrote a structural formula in
the prelab quiz
1,6-hexandiamine This is the same thing
as Hexane-1,6-diamine for which you wrote a
structural formula in the prelab quiz
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sebacoyl dichloride (decanedioyl dichloride) This
is the same thing as the 1,10-dichloro-1,10-dideca
nal for which you wrote a structural formula in
the prelab quiz

1,6-hexandiamine This is the same thing
as Hexane-1,6-diamine for which you wrote a
structural formula in the prelab quiz
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This kind of polymerization reaction in which
molecular growth occurs due to the interaction of
functional groups is called step growth
polymerization.
Another term for this class of reaction is
condensation polymerization. The term
condensation refers to the production of the
small byproduct HCl.
sebacoyl dichloride (decanedioyl dichloride)
covalent bond
1,6-hexandiamine
The byproduct of THIS reaction is hydrochloric
acid (HCl). Other step reactions produce
different byproducts.
Note You will learn more about reversible
reactions in the equilibrium unit later in the
semester.
HCl must be removed from the reaction container
to prevent decomposition (a reverse reaction).
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Polymerization is not just one reaction between
two molecules.
The reaction continues to covalently bond
molecules together into really long chains.
H Cl?
Noticeagainhow the reactions are all taking
place at the functional groups and NOT at the
hydrocarbon groups.
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The repeating unit in the polymer is usually
indicated in this manner.
A polymer such as this one which was synthesized
from 2 different monomers is called a copolymer.
This polymer is called nylon.
There are different forms of nylon. This
particular form is called nylon 6, 8 due to the
number of carbon atoms in the 2 copolymer parts
of the repeat unit.
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The long chains have a weak (side-to-side)
attractions to each other. Because there are so
many of them, however, the combination of these
bonds is quite strong.
The weak(side-to-side) attraction is called
hydrogen bonding.
The hydrogen bonds are NOT the same as covalent
bonds. These hydrogen bonds are illustrated here
as 3 dashed lines.
Note This is the same kind of attraction that
holds the 2 sides of DNA together.
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PET SynthesisExample of a step growth
polymerization
dimethyl isophthalate
hydroxyl or alcohol functional groups
ester functional groups
ethylene glycol
Guess where the reaction will take place?
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PET SynthesisExample of a step growth
polymerization
dimethyl isophthalate
esterification
ethylene glycol
A catalyst of some kind is needed to make this
reaction occur.
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Remember that this kind of polymerization
reaction with more than one monomer and a
byproduct is called a step growth reaction or
condensation reaction.
methanol byproduct
ester group
The byproduct of THIS reaction is methanol
(CH3OH).
Methanol must be removed from the reaction
container to prevent decomposition (a reverse
reaction).
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x
methanol byproduct A methanol molecule is formed
every time an ester linkage is formed.
repeat unit
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This kind of polymer is called a polyester
because the copolymersdimethyl isophthalate and
ethylene glycolform an ester linkage. Through
the structure, the ester is the highest priority
functional group and it repeats itself over and
over.
polyethylene terephthalate
PET
ester group
repeat unit
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Polyethelene SynthesisExample of chain growth
polymerization
ethylene (ethene)
Pay close attention to how the reaction takes
place between the functional groups. In this
case the reaction occurs between alkenyl groups
(i.e. between double bonds).
A catalyst of some kind is needed to make this
reaction occur.
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CH2
CH2
CH2
CH2
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This kind of polymerization reaction which has
just one type of monomer is called a chain
reaction. An older term for this class of
reaction is a addition reaction.
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Polymer Synthesis

• The BIG IDEA!
• From this activity
• You are NOT expected to understand all the
  intricacies of polymer synthesis.
• You ARE expected to understand from this activity
  that FUNCTIONAL GROUPS are the locations where
  reactions take place in organic chemical
  reactions.

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The End