Macromolecules

K Warne

C

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C

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C

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C

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C

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H

MacromoleculesWhat do you notice about this structure?

It is made of lots of small repeating units joined together?

C

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C

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C

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C

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C

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H

MacromoleculesThese large molecules are referred to as polymers. The repeating unit is usually derived from a small original molecule which is called the monomer?

C

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H

MacromoleculesThe small original molecule which makes this polymer is ethene.

The double bond breaks to form the bonds that link the individual units together. The polymer molecule can stretch up to hundreds or even thousands of units. The formation of a polymer from its monomers is known as polymerisation.

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MacromoleculesThe small original molecule which makes this polymer is ethene. The polymer is therefore poly(ethene) or polythene.

C

H

H

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H

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EtheneH

H

H

C CH

monomer

PolymerPoly(ethene)

(Ethene is usually drawn with bonds at 1200)

Macromolecules

K Warne

Macromolecule - Alternative term: polymer moleculeMolecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of (small) units derived, actually or conceptually, from molecules of low relative molecular mass.

Definition - Macromolecule

Note 1: In many cases, especially for synthetic polymers, a molecule can be regarded as having a high relative molecular mass if the addition or removal of one or a few of the units has a negligible effect on the molecular properties. This statement fails in the case of certain properties of macromolecules which may be critically dependent on fine details of the molecular structure, e.g., the enzymatic properties of polypeptides.

Note 2: If a part or the whole of the molecule has a high relative molecular mass and essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass, it may be described as either macromolecular or polymeric, or by polymer used adjectivally.

Note 3: In most cases, the polymer can actually be made by direct polymerization of its parent monomer but in other cases, e.g., poly(vinyl alcohol), the description conceptual � �denotes that an indirect route is used because the nominal monomer does not exist.

Source: IUPAC Polymer Education Website/Glossary: <http://www.iceb.ufop.br/dequi/iupac/polymerglossary/terms_search.php>

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MacromoleculesPoly(ethene) or polythene

C C

H

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H H

H

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n

Shorthand representations:

(–CH2 – CH2–)n

C C C C C C C C C C C

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H

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Macromolecules

K Warne

Alkenes

Esters

Amines

(alcohol)~yl

(acid)~oate

Amino -

CH3CONH2

Acylchlorides

Amides

~oyl Chloride

~amide

Aldehydes

Carboxylic Acids

~al

~oic acid

CH3-IHaloalkanes

Ketones

Halo~

~one

CH2 = CH2

Alcohols

~ene

~ol

Functional

groups

The functional

groups in a

molecule are

………………. or

………………….. of

atoms which

determine the

…………………….

of organic

molecules. 

Identify the functional group in each molecule below and move it to its appropriate box.

Macromolecules

K Warne

Alkenes CH2 = CH2 Ethene

EthanolAlcohols

~ene

~ol

CH3-IF - fluoro ~ Cl - chloro~ Br - bromo~

I - Iodo~

Propanone

Haloalkanes

Ketones

Halo~

~one

Ethanal

Ethanoic acid

Aldehydes

Carboxylic Acids

~al

~oic acid

Ethanoyl Chloride

CH3CONH2 Ethanamide

Acylchlorides

Amides

~oyl Chloride

~amide

Ethyl Ethanoate

Amino methane

Esters

Amines

(alcohol)~yl

(acid)~oate

Amino -

Functional groups

The functional groups in a molecule are

atoms or

combinations of atoms which determine the

properties of organic molecules. 

Not needed

Not needed

Macromolecules

K Warne

HOMOGENEOUS HETEROGENEOUS

A mixture with component parts that are

indistinguishable from each other.

A non-uniform mixture.

EXAMPLES Decide which of the following are heterogeneous and which are homogeneous.

The atmosphere, Oil & Water, Salt water, Hair Gel, Sand & Water, Milk, Iron filings & sulphur, Tea, smoke

Mixtures - Types

Macromolecules

K Warne

HOMOGENEOUS HETEROGENEOUS

A mixture with component parts that are

indistinguishable from each other.

A non-uniform mixture.

EXAMPLES

The Atmosphere Oil & water

Salt water Hair Gel

Milk Sand & water

Tea Iron & sulphur

smoke

Mixtures - Types

Macromolecules

K Warne

PolymerisationPolythene is formed via an addition reaction using free radical polymerisation. The reaction can be represented as:

• Reaction conditions: 2000 C, 2000 atmospheres, presence of oxygen initiator.• The reaction proceeds through a set of distinct steps: Initiation, Propagation & Termination• Each of these steps involves a molecule which has one unpaired electron known as a Free Radical (Ra●)

which is a highly reactive species.

1. Initiation:

2. Propagation:

3. Termination:

(n ~ 2000 – 20 000)

Mechanism adapted from: www.chemguide.co.uk/mechanisms/freerad/polym.htmlFor an in-depth discussion of this process see: http://www.materialsworldmodules.org/resources/polimarization/3-addition.html

The free radicals, Ra ● are produced by reaction between some of the ethene and the oxygen initiator. (The radical can take a number of forms and usually includes at least one oxygen atom.)R(O) Ra ●

A free radical joins an ethene molecule and a new longer free radical is formed.

Ra● + CH2=CH2 Ra CH2CH2

●

Ra CH2CH2●

+ CH2=CH2 RaCH2CH2CH2CH2● (each time the chain gets longer)

Two free radicals hit each other producing a final molecule.

Ra(CH2)n●

+ ● (CH2)mRa Ra(CH2)n ̶ (CH2)mCH2Ra (The process stops here because no new free radicals are formed.)

As chain termination is a random process, poly(ethene) will be made up of chains of a wide variety of different lengths.

(Radicals produced)

(Radicals produce more radicals)

(Two radicals combine)

MacromoleculesPolymerisation simulations

HO● + CH2=CH2 HOCH2CH2 ●

ROCH2CH2● + nCH2=CH2 RO(CH2CH2)nCH2CH2

●

View each of the simulations below (you may need to escape and review the page as slideshow a number of times) to decide which steps are Initiation, Propagation and/or Termination. Initiation Propagation Termination

HOCH2CH2● + ●CH2CH2OH HOCH2CH2CH2CH2OH

(Copy/paste or Drag & drop these labels)

MacromoleculesPolymerisation simulations

HO● + CH2=CH2 HOCH2CH2 ●

ROCH2CH2● + nCH2=CH2 RO(CH2CH2)nCH2CH2

●

View each of the simulations below (you may need to escape and review the page as slideshow a number of times) to decide which steps are Initiation, Propagation and/or Termination.

Initiation,

Propagation

PropagationTermination

Sources: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

HOCH2CH2● + ●CH2CH2OH HOCH2CH2CH2CH2OH

MacromoleculesCondensation Polymers

O

C C O

H

H

H H

C

O

C C O

H

H

H H

H

H

+ + H2O

Carboxylic acids can combine with alcohols to form esters.

This reaction is also known as condensation because water is produced.

Both carboxylic acids and alcohols can however have two functional groups per molecule. In this case the final products could react again and again...

O C

H

H

H

H

O

O C

O

C C O

H

C

H H

H

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OO C

H

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C

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OO C

H

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OO C

H

C

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H

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OO C

H

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C

H H

H

O

C

O

C C

H

C

HH

H

+ +

The chain length of the molecule increases and the resulting molecule can continue reacting to increasing the length of the chain further.

The CH2CH2 groups in these molecules could be replaced with larger chains or even other functional groups to create compounds with different properties...

(- H2O) (- H2O)

MacromoleculesEg: poly(ethylene terephthalate) - PET

Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester.

This one is called PET, which stands for poly(ethylene terephthalate).

poly(ethylene terephthalate) - PET

Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

PET is used to make soft-drink

bottles, magnetic tape, and many

other plastic products.

The next slide has an animation to show the formation of PET

MacromoleculesEg: poly(ethylene terephthalate) - PET

Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester.

This one is called PET, which stands for poly(ethylene terephthalate).

poly(ethylene terephthalate) - PET

Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

PET is used to make soft-drink

bottles, magnetic tape, and many

other plastic products.

MacromoleculesEg: poly(ethylene terephthalate) - PET

Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester.

This one is called PET, which stands for poly(ethylene terephthalate).

poly(ethylene terephthalate) - PET

Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

PET is used to make soft-drink

bottles, magnetic tape, and many

other plastic products.

Copy and paste the dotted red box

around each ester linkage.

MacromoleculesEg: poly(ethylene terephthalate) - PET

Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester.

This one is called PET, which stands for poly(ethylene terephthalate).

poly(ethylene terephthalate) - PET

Ester linkage

Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

PET is used to make soft-drink

bottles, magnetic tape, and many

other plastic products.

Copy and paste the dotted red box

around each ester linkage.

MacromoleculesNylon

A carboxylic acid monomer and an amine monomer can join in an amide linkage.

As before, a water molecule is removed, and an amide linkage is formed.

Notice that an acid group remains on one end of the chain, which can react with another amine monomer. Similarly, an amine group remains on the other end of the chain, which can react with another acid monomer.

Monomers can therefore continue to join by amide linkages to form a long chain. Because of the type of bond that links the monomers, this polymer is called a polyamide. The polymer made from these two six-carbon monomers is known as nylon-6,6. (Nylon products include hosiery, parachutes, and ropes.)

Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

Macromolecules

Kevlar is a polymer formed by joing the two monomers; benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene through an amide link.

Kevlar

+(- H2O)

Sources - Adapted from: http://www.chemguide.co.uk/organicprops/amides/polyamides.html

Kevlar’s strength is enhanced greatly by the presence of cross linking hydrogen bonding between the chains.

Macromolecules