Transcript Document

Unit 2
The World of Carbon
Menu
•
•
•
•
•
Fuels
Nomenclature
Reactions of Carbon Compounds
Polymers
Natural Products
Fuels
Crude oil
• Crude oil is a source of many
fuels.
• It is also the principal
feedstock for the manufacture
of petroleum-based consumer
products because these are
compounds of carbon.
Petrol
• Petrol can be produced by the reforming
of naphtha.
• Reforming alters the arrangement of
atoms in molecules without necessarily
changing the number of carbon atoms
per molecule.
•As a result of the reforming process,
petrol contains branched-chain alkanes,
cycloalkanes and aromatic hydrocarbons
as well as straight-chain alkanes.
Aromatic hydrocarbon
Branched-chain
hydrocarbon
Cycloalkane
• Any petrol is a blend of
hydrocarbons which boil at
different temperatures.
• A winter blend of petrol is different
from a summer blend. In winter
butane is added to petrol so that it
will catch fire more easily.
Engines
• In a petrol engine, the petrol-air
mixture is ignited by a spark.
• ‘Knocking’ is caused by auto-ignition.
• Auto-ignition is when the petrol-air mix
ignites too soon due to the heat from
the engine. This makes the engine
perform badly.
• Knocking is when the engine shakes and
shudders.
• The tendency of alkanes to autoignite used to be reduced by the
addition of lead compounds.
• Unfortunately the lead compounds
cause serious environmental
problems.
• Unleaded petrol uses components
which have a high degree of
molecular branching and/or
aromatics and/or cycloalkanes to
improve the efficiency of burning.
Alternative fuels
• Fossil fuels are going to run out in
the future.
• Fuels used produce carbon dioxide,
which increases the “greenhouse
effect”.
• We need other fuels which are
renewable and non-polluting.
• Sugar cane is a renewable source
of ethanol for mixing with petrol.
• Some biological materials,(i.e.
manure and straw) under
anaerobic conditions, ferment to
produce methane (biogas).
• Methanol is an alternative fuel to
petrol, but it has certain
disadvantages, as well as
advantages.
Methanol
• Almost complete
combustion
• No carcinogens
• Cheaper than
petrol
• Less explosive
than petrol
• Little modification
to car engine
• Difficult to mix
with petrol
• Very corrosive
• Toxic
• Larger fuel tanks
needed.
• Hydrogen could well be the fuel of
the future.
• If water can be electrolysed, using
a renewable energy source, such as
solar power, hydrogen will be
obtained.
• The hydrogen will burn, producing
water, and so will be pollution-free.
• The problem with hydrogen is
storing the gas in large enough
quantities.
Fuels
• Click to repeat Fuels
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• Click to End
Nomenclature &
Structural formula
Nomenclature
• Nomenclature means the way
chemical compounds are given
names.
• These names are produced by a
special system.
Naming organic
compounds
• All organic compounds belong to
“families” called homologous
series.
• A homologous series is a set of
compounds with the same general
formula, similar chemical
properties and graded physical
properties.
• Most homologous series have a
special functional group.
• A functional group is a reactive
group of atoms which are attached
to the carbon chain.
• The functional group is the part of
the molecule where most reactions
take place.
Functional Groups
Functional
Group
none
Name of
Group
Homologous
series
Alkanes
C
C
Double bond
Alkenes
C
C
Triple bond
Alkynes
Hydroxyl
Alkanols
(Alcohols)
O H
Functional Groups
Functional
Group
C
H
Name of
Group
Carbonyl
O
Carbonyl
C
O
C
OH
Carboxylic
O
NH2
Amine
Homologous
series
Alkanals
(Aldehydes)
Alkanones
(Ketones)
Alkanoic
acids
Amines
• The first part of the compound’s
name is decided by the number of
carbon atoms in the molecule.
• The second part of the name is
decided by the homologous series to
which the compound belongs.
Number
of C
atoms
1
First part Number
of name of C
atoms
meth5
First part
of name
2
eth-
6
hex-
3
prop-
7
hept-
4
but-
8
oct-
pent-
2nd Part of Name
Homologous
series
Alkanes
General
Formula
CnH 2n+2
Name ending
Alkenes
CnH 2n
…ene
Alkynes
CnH 2n-2
…yne
Alkanols
CnH 2n+1OH
…anol
…ane
2nd Part of Name
Homologous
series
Alkanals
General
Formula
CnH 2n+2
Name ending
Alkanones
CnH 2n
…anone
Alkanoic
acids
Amines
CnH 2n-2
…anoic acid
CnH 2n+1OH
…ylamine
…anal
• This method works well for
straight-chain hydrocarbons.
• Here is an example: hexane
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
• We have to add rules to help deal
with branched chains.
H
H
H
H
H
CH3 H
C
C
C
C
C
H
H
CH3 H
C
CH3 H
H
• First draw out the full structure.
H
H
H
H
H
CH3 H
C
C
C
C
C
H
H
CH3 H
C
CH3 H
H
• Number the atoms in the longest
continuous carbon chain.
• Start at the end nearer most
groups.
H
H
C
H
H
6
C
5
H
H
C
4
H
3
C
CH3 H
CH3 H
C
2
1
C
CH3 H
H
• This now gives us the basic name –
in this case hexane.
H
H
C
H
H
6
C
5
H
H
C
4
H
3
C
CH3 H
CH3 H
C
2
1
C
CH3 H
H
• You must now identify any side
chains.
• -CH3 is methyl
• -CH2CH3 is ethyl
• Now identify and count the number
and type of side chain.
• di - shows 2
• tri – shows 3
• tetra – shows 4
• Label the carbon atom(s) they join
• This now gives us the full name:
• 2,2,4 trimethylhexane.
H
H
C
H
H
6
C
5
H
H
C
4
H
3
C
CH3 H
CH3 H
C
2
1
C
CH3 H
H
• Naming other homologous series
works in the same way.
• With those we start numbering at
the end nearer the functional
group e.g. this alkene:
H
H
H
H
H
CH3
H
C
C
C
C
C
C
H
C2H5 CH3 H
H
• Number the atoms in the longest
carbon chain.
H
H
C
H
1
H
C
H
2
C
H
3
4
C
CH3
C
5
H
C
6
C2H5 CH3 H
H
• This now gives us the basic name –
in this case hex-2-ene.
H
H
C
H
1
H
C
H
2
C
H
3
4
C
CH3
C
5
H
C
6
C2H5 CH3 H
H
• Identifying the side chains gives us
the full name:
• 5,5 dimethy 4 ethyl hex-2-ene.
H
H
C
H
1
H
C
H
2
C
H
3
4
C
CH3
C
5
H
C
6
C2H5 CH3 H
H
• We can use the
same principles
with cyclic
hydrocarbons.
H
H
H
H
C
C
H
H
C
C
H
C
CH3
H
H
• 1 methyl
cyclopentane
H
H
H
H
C
3
C 4
H
5
C
H
2 C
1
C
CH3
H
H
H
Isomers H
• Isomers are
compounds with
the same
molecular formula
but different
structural
formulae
• For example C4H10
H
C
H
H
H
C
C
C
H
H
H H H
butane
H H H
H
C
H
H
C
C
C
H
H
H
H
2 methyl propane
Alcohols
• The alcohols form another
homologous series – called the
alkanols.
• We can recognise the alkanols
because they contain an OH group.
• They are given names as if they are
substituted alkanes.
• 3 methyl pentan-2-ol
H
H
C
5
H
H
C
4
H
CH3 H
C
3
H
C
2
H
1
C
OH H
H
Aldehydes
• The aldehydes form another
homologous series – called the
alkanals.
• We can recognise the alkanals
because they contain a carbonyl
group at the end of the carbon
chain.
• They are named as if they are
substituted alkanes.
• 3,4 dimethyl pentanal
• We don’t need to number the
carbonyl group because it must be
on the first carbon.
H
H
C
5
H
H
C
4
CH3 H
C
CH3 H
3
C
2
H
H
1
C
O
Ketones
• The ketones form another
homologous series – called the
alkanones.
• We can recognise the alkanones
because they contain a carbonyl
group in the middle of the carbon
chain.
• They are named as if they are
substituted alkanes.
• 3,3 dimethyl pentan-2-one
H
H
C
5
H
H
C
4
H
CH3
C
3
H
C
2
CH3 O
1
C
H
H
Alkanoic acids
• The alkanoic acids form another
homologous series.
• Carboxylic acids are used in a
variety of ways.
Alkanoic acids
• We can recognise the alkanoic
acids because they contain a COOH
group.
C
O
OH
• We can name the alkanoic acids
using the principles we have used
before.
H
H
H
CH3 H
H
C
C
C
C
C
C
H
H
H
H
H
O
OH
• 4 methyl hexanoic acid
• We don’t need to number the acid
group because it must be on the
first carbon.
H
H
H
6 5
C
C
CH3 H
4
3
C
C
H
2
C
1
C
H
H
H
O
H
H
OH
Esters
• An ester can be identified the
‘-oate’ ending to its name.
• The ester group is:
C
O
O
Esters
• An ester can be named given the
names of the parent alkanol and
alkanoic acid.
• The name also tells us the alkanoic
acid and alkanol that are made
when the ester is broken down.
The acid and alkanol combine
CH3 CH2 C OH
O
The acid and alkanol combine
HO CH3
The acid and alkanol combine
CH3 CH2 C OH
HO CH3
O
Water is formed.
CH3 CH2 C O CH3
O
H2 O
Naming esters
Acid name
Alkanol name
Ester name
ethanoic acid
methanol
methyl
ethanoate
ethyl
propanoate
propyl
butanoate
butyl
methanoate
propanoic acid ethanol
butanoic acid
propanol
methanoic acid butanol
• A typical ester is shown below.
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
• We can identify the part that came
from the alkanoic acid – propanoic
acid.
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
• We can identify the part that came
from the alkanol - ethanol
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
• This gives us the name
ethyl propanoate
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
Aromatic Hydrocarbons
• Benzene is the simplest aromatic
hydrocarbon.
• It has the formula C6H6.
• The benzene molecule has a ring
structure.
• Even though benzene would seem
to be unsaturated it does not
decolourise bromine water.
• All the bonds in benzene are
equivalent to each other – it does
not have the usual kind of single
and double bonds.
• The bonds in benzene are
intermediate between single and
double bonds.
• Their lengths and bond energies
are in between those of single and
double bonds.
• The stability of the
benzene ring is due
to the
delocalisation of
electrons.
• A benzene ring in
which one
hydrogen atom has
been substituted by
another group is
known as the
phenyl group.
• The phenyl group
has the formula C6H5.
Benzene and its related compounds are
important as feedstocks.
One or more hydrogen atoms of a benzene
molecule can be substituted to form a range of
consumer products.
Nomenclature and
Structural Formula
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Structural Formula
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Reactions of
Carbon
Compounds
Saturated Hydrocarbons
• Alkanes and cycloalkanes are
saturated hydrocarbons.
• Saturated hydrocarbons contain
only carbon to carbon single
covalent bonds.
Unsaturated Hydrocarbons
• The alkenes are unsaturated
hydrocarbons.
• Unsaturated hydrocarbons contain
at least one carbon to carbon
double covalent bond.
Addition Reactions
• Addition reactions take place when
atoms, or groups of atoms, add
across a carbon to carbon double
bond or carbon to carbon triple
bond.
• For alkenes the basic reaction
is:
H
H
C
C
+ *
*

H
H
C
C
*
*
• When bromine adds to an alkene
we have an addition reaction.
• C4H8 + Br2  C4H8 Br2
H
H
C
C
+ Br
Br

H
H
C
C
Br Br
• The addition reaction between
hydrogen chlkoride and an alkene
gives the equivalent alkyl
chloride.
• C3H6 + HCl  C3H7Cl
propene + hydrogen chloride  propyl chloride
H
H
C
C
+ H
Cl

H
H
C
C
H
Cl
Halogenoalkanes
• Halogenoalkanes have properties which
make them useful in a variety of
consumer products.
• In the atmosphere, ozone, O3, forms a
protective layer which absorbs
ultraviolet radiation from the sun.
• The depletion of the ozone layer is
believed to have been caused by the
extensive use of certain CFCs
(chlorofluorocarbons).
• The addition reaction between
water and an alkene gives the
equivalent alkanol.
• propene + water  propanol
• C3H6 + H2O  C3H7OH
H
H
C
C
+ H 2O

H
H
C
C
H
OH
Sometimes addition reactions can
give two different isomeric products.
CH2=CH-CH3
HCl
CH2Cl-CH2-CH3
CH3-CHCl-CH3
Ethanol
• To meet market demand ethanol is
made by means other than
fermentation.
• Industrial ethanol is manufactured
by the catalytic hydration of ethene.
H
H
H
C
C
H + H 2O

H
H
H
C
C
H
OH
H
• Ethanol can be converted to ethene
by dehydration.
• This reaction uses aluminium oxide
or concentrated sulphuric acid as a
catalyst.
H
H
H
C
C
H
H
OH
H
H
 C
C
H
H
+
H2O
• For alkynes the reaction
takes place in two stages:
C
*
C
C
+ *
*

*
C
+ *
*

C
C
*
*
*
*
C
C
*
*
With hydrogen:
CH
CH
H2
CH2
CH2
H2
CH3
CH3
With a halogen:
CH
CH
X2
CHX
CHX
X2
CHX2
CHX2
With a halogen halide:
CH
CH
HX
CHX
CH2
HX
CHX2
CH3
CH2X
CH2X
The benzene ring resists any addition
reactions.
Its delocalised electrons mean
that its bonds do not behave like
the bonds in an unsaturated
compound
Alcohols
•
•
•
•
There are three types of alcohols:
Primary
Secondary
Tertiary
Primary Alcohols
• Primary alcohols have at least two
hydrogen atoms on the carbon
atom carrying the OH group.
H
C
H
OH
Secondary Alcohols
• Secondary alcohols have one
hydrogen atom on the carbon atom
carrying the OH group.
H
C
OH
Tertiary Alcohols
• Tertiary alcohols have at no
hydrogen atoms on the carbon
atom carrying the OH group.
C
OH
Oxidation and Reduction
• Oxidation and reduction can be
described in terms of loss or gain
of electrons.
• In organic chemistry it is more
useful to describe them differently.
• Oxidation is an increase in the
oxygen to hydrogen ratio e.g.
CH3CH2OH  CH3CHO
1:6
1:4
• Reduction is a decrease in the
oxygen to hydrogen ratio.
CH3CO2H  CH3CH2OH
2:4
1:6
Oxidation Reactions
• The simplest oxidation reaction of
alcohols is when they are burned in
oxygen, giving carbon dioxide and
water.
• Some alcohols can be oxidised to
give aldehydes and ketones.
• Primary alcohols can be oxidised in
two stages : first to an aldehyde
H
H
R C O H
H
Primary alcohol
R C O

Aldehyde
• Primary alcohols can be oxidised in
two stages : first to an aldehyde
and then to an alkanoic acid.
H
H
R C O H
H
Primary alcohol
R C O

Aldehyde
H
OH
R C O
R C O
Aldehyde

Alkanoic Acid
• Secondary alcohols can be oxidised
only once: to a ketone
R*
R*
R C O H
H
Secondary alcohol
R C O

Ketone
No further oxidation is possible
• Tertiary alcohols cannot be
oxidised at all.
R*
R C O H
R**
No oxidation is possible
• Aldehydes can be oxidised to give
carboxylic (alkanoic) acids while
ketones cannot.
• This can be used as a means of
differentiating between aldehydes
and ketones.
• The oxidising agents that are used
most often give visible signs of
reaction.
Reagent
Visible effect
Acidified permanganate
Purple  colourless
Acidified dichromate
Orange  green
Copper oxide
Black  brown
Tollen’s Reagent
Fehling’s solution
Silver mirror
produced
Blue  red
Benedict’s solution
Blue  red
Condensation Reactions
• In a condensation reaction, the
molecules join together by the
reaction of the functional groups to
make water.
H HO
H2 O
Esters
• Esters are formed by the
condensation reaction between a
carboxylic acid and an alcohol.
• Uses of esters include flavourings,
perfumes and solvents.
Esters
• Esters can be recognised by the
ester link shown below:
C
O
O
• The ester link is formed by the
reaction of a hydroxyl group of an
alkanol with a carboxyl group of a
carboxylic acid.
HO
H
H
C
C
H
H
H
• The ester link is formed by the
reaction of a hydroxyl group of an
alkanol with a carboxyl group of a
carboxylic acid.
HO
H
H
C
C
H
H
H
• The ester link is formed by the
reaction of a hydroxyl group of an
alkanol with a carboxyl group of a
carboxylic acid.
H
H
H
O
C
C
C
H
H
O
H
• The ester link is formed by the
reaction of a hydroxyl group of an
alkanol with a carboxyl group of a
carboxylic acid.
H
H
H
O
C
C
C
H
H
O
H
H
H
H
O
C
C
C
H
H
Carboxylic acid
O
H
HO
H
H
C
C
H
H
Alkanol
H
H
H
H
O
C
C
C
H
H
O
H
HO
H
H
C
C
H
H
H
H
H
H
O
C
C
C
H
H
O
H
HO
H
H
C
C
H
H
H
Water is formed from hydrogen of one molecule
and hydroxide from the other.
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
H2 O
Water is formed from hydrogen of one molecule
and hydroxide from the other.
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
H2 O
Water is formed from hydrogen of one molecule
and hydroxide from the other.
The remains of the molecules join together
H
H
H
O
C
C
C
H
H
O
H
H
C
C
H
H
H
H2 O
Water is formed from hydrogen of one molecule
and hydroxide from the other.
The remains of the molecules join together
Hydrolysis Reactions
• In a hydrolysis reaction, a
molecule is split up by adding the
elements of water.
H HO
H2 O
• The carboxylic acid and the alcohol
from which the ester are made can
be obtained by hydrolysis.
CH3CH2COOCH3
+ H2O
CH3CH2COOH
+ CH3OH
• The formation and hydrolysis of an
ester is a reversible reaction.
condensation
Ester + water
Acid + alkanol
hydrolysis
Yields
• If we write the equation for a
reaction we can calculate what
mass of product should be
produced – the theoretical yield.
• When we carry out the experiment
we can measure the mass of
product produced – the actual
yield.
Percentage Yield
• Percentage yield is the actual yield,
expressed as a percentage of the
theoretical yield.
Percentage
Yield
=
Actual Yield
100
X
Theoretical Yield
1
Percentage
Yield
=
Actual Yield
100
X
Theoretical Yield
1
Titanium dioxide, TiO2, is used in the manufacture of
white paint. It is made from ilmenite, FeTiO3.
If 45.1kg of TiO2 is obtained from 100kg of ilmenite,
what is the percentage yield of the conversion?
FeTiO3

TiO2
1 mole  1 mole
152g  80g
1g  80/152g = 0.5263g
100kg  52.63kg
Percentage yield = 45.1 x 100 = 85.7%
52.63
1
Reactions of Carbon
Compounds
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Carbon Compounds
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Polymers
Addition Polymerisation
• Many polymers are made from the small
unsaturated molecules, produced by the
cracking of oil.
• They add to each other by opening up
their carbon to carbon double bonds.
• This process is called addition
polymerisation.
• Ethene is a starting material of major
importance in the petrochemical industry
especially for the manufacture of plastics.
• It is formed by cracking the ethane from the
gas fraction or the naphtha fraction from oil.
• Propene can be formed by cracking the
propane from the gas fraction or the naphtha
fraction from oil.
I*
H
H
C
C
H
H
The ethene is attacked by an initiator (I*) which
opens up the double bond
I
H
H
H
H
C
C* C
C
H
H
H
H
The ethene is attacked by an initiator (I*) which
opens up the double bond
Another ethene adds on.
I
H
H
H
H
H
H
C
C
C
C*
C
C
H
H
H
H
H
H
The ethene is attacked by an initiator (I*) which
opens up the double bond
Another ethene adds on.
Then another
I
H
H
H
H
H
H
C
C
C
C
C
C*
H
H
H
H
H
H
The ethene is attacked by an initiator (I*) which
opens up the double bond
Another ethene adds on.
Then another
….
Naming polymers
• The name of the polymer is derived from
its monomer.
MONOMER
POLYMER
***ene
poly(***ene)
ethene
poly(ethene)
propene
poly(propene)
styrene
poly(styrene)
chloroethene
poly(chloroethene)
tetrafluoroethene poly(tetrafluoroethene)
Repeat Units
• You can look at the structure of an
addition polymer and work out its
repeat unit and the monomer from
which it was formed.
• The repeat unit of an addition
polymer is always only two carbon
atoms long.
-CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -
-CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 Repeat Unit CH2 -CH2
Monomer CH2 =CH2
-CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl Repeat Unit CH2 -CHCl
Monomer CH2 =CHCl
Condensation Polymers
• Condensation reactions involve
eliminating water when two
molecules join.
• Condensation polymers are made
from monomers with two
functional groups per molecule.
• Normally there are two different
monomers which alternate in the
structure e.g.
H
H
and
HO
OH
• The molecules join together,
eliminating water as they do so.
• Hydrogen comes from one
molecule.
• Hydroxide comes from the other
molecule.
• The molecules join where these
groups have come off.
H
HO H
OH
HOH
H
H2 O
H
HOH
H
H2 O
H2 O
OH
H
H OH
H2 O
H2 O
H2 O
H
H
HOH
H2 O
H2 O
H2 O
H2 O
O
OH
H
H2 O
H2 O
H2 O
H2 O
H2 O
Repeat Units
• You can look at the structure of a
condensation polymer and work
out its repeat unit and the
monomers from which it was
formed.
Polymer
-C-(CH2)4-C-N-(CH2)6-N -C-(CH2)4-C-N-(CH2)6-N-
O
OH
H O
OH
H
Repeat Unit
-C-(CH2)4-C-N-(CH2)6-N -C-(CH2)4-C-N-(CH2)6-NO
OH
H O
-C-(CH2)4-C-N-(CH2)6-NO
OH
H
Monomers
HO-C-(CH2)4-C-OH
and
O
O
OH
H
H-N-(CH2)6-N-H
H
H
Polymer
-O-C-C6H4-C-O-CH2-CH2 -O-C-C6H4-C-O-CH2-CH2O
O
0
O
Repeat Unit
-O-C-C6H4-C-O-CH2-CH2 -O-C-C6H4-C-O-CH2-CH2-
O
O
-O-C-C6H4-C-O-CH2-CH2-
0
O
O
O
Monomers
H-O-C-C6H4-C-O-H
O
O
and
HO-CH2-CH2 -OH
Condensation Polymers
• Typical condensation polymers are
polyesters and polyamides.
• Terylene is the brand name for a
typical polyester.
Polyesters
• As the name suggests polyesters
are polymers which use the ester
link.
• The two monomers which are used
are a diacid and a diol.
The diacid will have a typical structure:
C-O-H
H-O-C
O
O
The diol will have a typical structure:
HO
OH
They combine like this:
H-O-C
O
C-O-H
O
The diacid will have a typical structure:
C-O-H
H-O-C
O
O
The diol will have a typical structure:
HO
OH
They combine like this:
H-O-C
O
C-O-H
HO
O
OH
The diacid will have a typical structure:
C-O-H
H-O-C
O
O
The diol will have a typical structure:
HO
OH
They combine like this:
H-O-C
O
C-O
O
OH
H-O-C
O
C-O-H
O
The diacid will have a typical structure:
C-O-H
H-O-C
O
O
The diol will have a typical structure:
HO
OH
They combine like this:
H-O-C
O
C-O
O
O-C
O
C-O-H
HO
O
OH
The diacid will have a typical structure:
C-O-H
H-O-C
O
O
The diol will have a typical structure:
HO
OH
They combine like this:
H-O-C
O
C-O
O
O-C
O
C-O
O
OH
• Polyesters are manufactured for use
as textile fibres and resins.
• Polyesters used for textile fibres
have a linear structure.
• Cured polyester resins have a threedimensional structure. Cross linking
between the polyester chains makes
the structure much more rigid.
Amines
• Amines are a homologous series
containing the amine group:
N
H
H
The amide link
• The amide link is formed when an
acid and amine join together.
N
H
H
HO C
O
The amide link
• The amide link is formed when an
acid and amine join together.
N HO
H C
H
O
The amide link
• The amide link is formed when an
acid and amine join together.
N
C
H
O
H 2O
The amide link
• The amide link is formed when an
acid and amine join together.
N
C
H
O
The amide link
Polyamides
• A polyamide is made from a
diamine and a diacid:
H
N
N
H
C-O-H
H-O-C
H
H
diamine
They combine like this:
O
O
diacid
H
N
NH-O-C
H
H
H
O
C-O-H
O
H
N
N
C
C-O-H
H N
N
H
H
O
O
H
H2 O
H
H
H
N
N
C
C N
N H-O-C
H
C-O-H
H
H
O
O H
H
O
H2 O
H2 O
O
H
N
N
C
C N
N
C
C-O-H
H
H
O
O H
H
O
O
H2 O
H2 O
H2 O
• Nylon is a typical polyamide.
• Nylon is a very important
engineering plastic.
• The strength of nylon is caused by
hydrogen bonding between the
polymer chains.
Synthesis gas
• Synthesis gas can be obtained by
steam reforming of methane from
natural gas.
CH4 + H2O  CO + 3H2
• It can also be made by the steam
reforming of coal.
• Methanol, used in the production of
methanal, is made industrially from
synthesis gas.
• Methanal is an important feedstock
in the manufacture of
thermosetting plastics.
• It is used to assist cross-linking so
as to make thermosetting plastics
and resins.
New polymers
• Kevlar is an aromatic polyamide
which is extremely strong because
of the way in which the rigid, linear
molecules are packed together.
• These molecules are held together
by hydrogen bonds.
• Kevlar has many important uses.
• Poly(ethenol) is a plastic which
readily dissolves in water. It has
many important uses
• It is made from another plastic by a
process known as ester exchange.
• The percentage of acid groups
which have been removed in the
production process affects the
strengths of the intermolecular
forces upon which the solubility
depends.
• Poly(ethyne) can be treated to
make a polymer which conducts
electricity.
• The conductivity depends on
delocalised electrons along the
polymer chain.
• Poly(vinyl carbazole) is a polymer
which exhibits photoconductivity
and is used in photocopiers.
• Biopol is an example of a
biodegradable polymer.
• The structure of low density
polythene can be modified during
manufacture to produce a
photodegradable polymer.
Polymers
• Click to repeat Polymers
• Click to return to the Menu
• Click to End
Natural
Products
Fats and Oils
• Natural fats and oils can be
classified according to where they
come from:
• Animal
• Vegetable
• Marine
• Fats and oils in the diet supply the
body with energy.
• They are a more concentrated source
of energy than carbohydrates.
• Oils are liquids and fats are solids.
• Oils have lower melting points than
fats.
• This is because oil molecules have a
greater degree of unsaturation.
Saturated fats:
have more regular shapes than unsaturated oils:
Fat molecules close pack together
easily and have a low melting point
Oil molecules do not close pack together
so easily and have a high melting point
Oils can be converted into hardened
fats by adding of hydrogen.
H2
H2
H2
Oils can be converted into hardened
fats by adding of hydrogen.
This is how margarine is made
Fatty acids
• Fatty acids are straight chain
carboxylic acids, containing even
numbers of carbon atoms from C4
to C24, primarily C16 and C18.
• Fatty acids may be saturated or
unsaturated.
• Fats and oils are esters.
• They are made from the triol glycerol
(propan-1,2,3-triol)
and fatty acids.
CH2 OH
R C OH
CH
O
fatty acid
OH
CH2 OH
glycerol
• Fats and oils are esters.
• They are made from the triol glycerol
(propan-1,2,3-triol)
and fatty acids.
CH2 OH
CH
OH
CH2 OH
glycerol
HO C R
O
fatty acid
Three fatty acids form esters with the three OH
groups of glycerol.
HO C R1
CH2 OH
CH
O
HO C R2
OH
CH2
O
OH
HO C R3
O
Three fatty acids form esters with the three OH
groups of glycerol.
CH2 O
C R1
CH
O
O C R2
CH2
O
O C R3
O
• The hydrolysis of fats and oils
produces fatty acids and glycerol in
the ratio of three moles of fatty acid
to one mole of glycerol.
CH2 O
C R
CH
O
O C R
CH2
O
O C R
O
CH2 OH
CH
OH
CH2 OH
+ 3 R C OH
O
Fats and oils
• Fats and oils consist largely of
mixtures of triglycerides.
• The three fatty acid molecules
combined with each molecule of
glycerol need not be the same.
• Soaps are produced by the
hydrolysis of fats and oils.
Proteins
• Nitrogen is needed to make protein
in plants and animals.
• Proteins are condensation
polymers made up of many amino
acid molecules linked together.
• The structure of the protein is
based on the constituent amino
acids.
Amino acids
• These are compounds which
contain an amine group and an
acid group.
R
HO C C
N
O H
H
H
R
HO C C
N
O H
H
H
• There are about 25 essential amino
acids.
• They are different because they
have different side groups – shown
by “R”.
• Condensation of amino acids
produces the peptide (amide) link.
The peptide link
• The peptide link is formed when an
acid and amine join together. (We
have previously called this the
amide link.)
R1
HO C C
O H
R2
N HO
H C C
N
H
H
O H
H
The peptide link
• The peptide link is formed when an
acid and amine join together. (We
have previously called this the
amide link.)
R1
HO C C
O H
peptide
R2
link
N
C C
N
H O H
H
H
Amino acids polymerising
R1
HO C C
O H
R2
N HO
H C C
N
H
H
O H
H
Amino acids polymerising
R2
R1
HO C C
O H
N
C C
H O H
H2O
R3
N HO
H C C
N
H
H
O H
H
Amino acids polymerising
R2
R1
HO C C
O H
N
C C
H O H
H2 O
R4
R3
N
C C
H O H
H2 0
N HO
H C C
N
H
H
O H
H
Amino acids polymerising
R2
R1
HO C C
O H
N
C C
H O H
H2 O
R3
N
C C
H O H
H2 0
R4
N
C C
N
H O H
H
H2 O
H
Building proteins
• Proteins specific to the body’s
needs are built up within the body.
• The body cannot make all the
amino acids required for body.
• We need protein in our diet to
supply certain amino acids known
as essential amino acids.
Digestion
• During digestion enzymes
hydrolyse the proteins in our diet
to produce amino acids.
• The body then builds up the amino
acids it needs from those amino
acids.
R2
R1
HO C C
O H
N
C C
H O H
R3
R4
C C
NH2O
C C
N
H O H
H O H
H
N
H
R4
R2
R1
HO C C
O H
N
O H
H
R3
C C
NH2OC C
N
H O H
H O H
H
N
HO C C
H
H
R4
R1
HO C C
N
O H
H
R2
HO C C
NH2O
C C
N
O H
H O H
H
H
R3
HO C C
N
O H
H
H
H
R1
R4
HO C C
N
O H
H
H
HO C C
N
O H
H
R2
HO C C
N
O H
H
H
R3
HO C C
N
O H
H
H
H
Hydrolysis
• The structural formulae of amino
acids obtained from the hydrolysis
of proteins can be identified from
the structure of a section of the
protein as shown in the last few
slides.
Types of proteins
• Proteins can be classified as
fibrous or globular.
• Fibrous proteins are long and thin
and are the major structural
materials of animal tissue –
muscles, tissues etc.
• Globular proteins have the spiral
chains folded into compact units.
• Globular proteins are involved in
the maintenance and regulation of
life processes and include enzymes
and many hormones, eg insulin
and haemoglobin.
Enzymes
• Enzymes, such as amylase, are
biological catalysts
• An enzyme will work most
efficiently within very specific
conditions of temperature and pH.
• The further conditions are removed
from the ideal the less efficiently
the enzyme will perform.
• What an enzyme can do is related to
its molecular shape.
• Denaturing of a protein involves
physical alteration of the molecules
as a result of temperature change or
pH change.
• The ease with which a protein is
denatured is related to the fact that
enzymes are very sensitive to
changes in temperature and pH.
Natural Products
• Click to repeat Natural Products
• Click to return to the Menu
• Click to End
The End
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