Transcript Document

Unit 2
Carbon compounds
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title.
• Fuels
• Nomenclature and structural formula
• Reactions of carbon compounds
• Plastics and synthetic fibres
• Natural products
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Fuels
Fuels
• A fuel is a chemical which burns,
releasing energy.
• Combustion is another word for
burning, the reaction of a
substance with oxygen, in which
energy is given out.
Hydrocarbons
• The chemical compounds which
are found in oil and natural gas are
mainly hydrocarbons.
• A hydrocarbon is a compound
which contains hydrogen and
carbon only.
• Hydrocarbons burn in a plentiful
supply of air to produce carbon
dioxide and water.
• The test for carbon dioxide is that
it turns lime water milky.
To pump
Burning candle
Anhydrous
copper
sulphate
(turns blue)
Lime water
(turns cloudy)
Incomplete Combustion
• When fuels burn in a limited supply
of air then incomplete combustion
takes place and the poisonous gas,
carbon monoxide (CO) is produced.
• Increasing the amount of air used
to burn fuel improves efficiency
and decreases pollution.
Other products of
combustion
• Fossil fuels contain sulphur which
produces sulphur dioxide when the
fuel is burned.
• The oil industry tries to remove
this sulphur from the fuels before
selling them.
Nitrogen does not
react well because of
its strong bonds.
If there is a high
temperature the
nitrogen and oxygen
will combine to
make nitrogen
oxides.
The experiment
opposite shows how a
high voltage spark,
like one provided by
the spark plug or
lightning will do the
same.
High
Voltage
spark
Air
+
-
Nitrogen does not
react well because of
its strong bonds.
If there is a high
temperature the
nitrogen and oxygen
will combine to
make nitrogen
oxides.
The experiment
opposite shows how a
high voltage spark,
like one provided by
the spark plug or
lightning will do the
same.
High
Voltage
spark
Air
Brown
gas
+
-
Atmospheric Pollution
• The sulphur and nitrogen oxides
produced can dissolve in water,
making acid rain.
• Unburnt hydrocarbons escaping
from car exhausts can help cause
the destruction of the ozone layer.
Reducing Pollution
• Air pollution caused by burning
hydrocarbons can be reduced by:
using a special exhaust system – a
catalytic converter, in which metal
catalysts (platinum or rhodium)
will convert pollutants into
harmless gases.
altering the fuel to air ratio.
Pollution
• Soot particles produced by the
incomplete combustion of diesel
are harmful.
Oil
• Crude oil is a mixture of chemical
compounds (mainly hydrocarbons)
which can be to split it into
fractions.
• Oil can be separated into fractions
by the process of fractional
distillation.
Oil
• A fraction is a group of chemical
compounds, all of which boil within
the same temperature range.
Fractional Distillation of Oil
gases
(gaseous fuel)
petrol (gasoline)
(petrol)
naphtha
(chemicals)
Heated
oil from
furnace
paraffin (kerosine)
(aircraft fuel)
diesel
(fuel for lorries etc.)
residue (wax, tar)
Oil Fractions
Name
Uses
Gases
Carbon atoms
per molecule
1 to 4
Petrol
4 to 9
Fuel for cars
Naphtha
8 to 14
Chemicals
Paraffin
10 to 16
Aircraft fuel
Diesel
15 to 20
Lorry fuel
Residue
More than 20
Lubricating oil,
tar, wax etc.
Fuel
• Viscosity is a measure of the
thickness of a liquid.
• Flammability is a measure of easily
the liquid catches fire.
• As the boiling point of a fraction
increases then:
• it will not evaporate as easily.
• it will be less flammable
• it will be more viscous (thicker).
• Moving through the fractions from
gases to the residue
• The molecules present in the
fraction are longer and heavier
• They will find it more difficult to
become a gas i.e. they will be less
easy to evaporate.
• Moving up the fractions from gases to
the residue
• Since combustion involves the reaction
of gas molecules with oxygen
flammability will decrease.
• Increased molecular lengths mean that
molecules become more "tangled up",
so the liquid will become thicker (more
viscous).
Fuels
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Nomenclature &
Structural formula
Nomenclature
• Nomenclature means the way
chemical compounds are given
names.
• These names are produced by a
special system.
Naming hydrocarbons
• All hydrocarbons belong to
“families” called homologous
series.
• A homologous series is a set of
compounds with the same general
formula and similar chemical
properties.
Homologous
Series
General
formula
Name
alkanes
CnH2n+2
….ane
alkenes
CnH2n
….ene
cycloalkanes CnH2n
cyclo….ane
• The other part of the name tells us
how many carbon atoms are
present.
Number
of C
atoms
1
name
name
meth-
Number
of C
atoms
5
2
eth-
6
hex-
3
prop-
7
hept-
4
but-
8
oct-
pent-
• This method works well for
straight-chain hydrocarbons like
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 nearest 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 alkenes works in the same
way, except we start numbering at
the end nearer the double bond.
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
Alkanols
• The alkanols form another
homologous series.
• We can recognise the alkanols
because they contain an OH group.
• We can name the alkanols using
the principles we have used before.
H
H
H
CH3 H
H
C
C
C
C
C
H
H
H
OH H
H
• 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
Alkanoic acids
• The alkanoic acids form another
homologous series.
• 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
Nomenclature and
Structural Formulae
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and Structural Formulae.
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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.
• It is possible to distinguish an
unsaturated hydrocarbon from a
saturated hydrocarbon using
bromine solution (bromine water).
• Take some
bromine solution
(brown) in test
tube.
• Add a few drops
of an unsaturated
hydrocarbon.
• Unsaturated
hydrocarbons
decolourise
bromine water.
colourless
Addition Reactions
• Addition reactions take place when
atoms, or groups of atoms, add
across a carbon to carbon double
bond.
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 and an alkene gives the
equivalent alkane.
• propene + hydrogen  propane
• C3H6 + H2  C3H8
H
H
C
C
+ H
H

H
H
C
C
H
H
• 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
Cracking Hydrocarbons
• Fractional distillation of crude oil
yields more long-chain
hydrocarbons than are needed by
industry.
• Cracking is an industrial method
for producing a mixture of smaller,
more useful molecules, some of
which are unsaturated.
mineral wool
soaked in oil
catalyst
heat
gas
Cracking
• The cracking process can be
carried out in different ways.
• Thermal cracking is where heat is
used to split large molecules into
smaller ones.
• Catalytic cracking is where a
catalyst is used to split large
molecules into smaller ones.
Catalytic Cracking
• A catalyst allows the reaction to take
place at a lower temperature.
• Cracking can be carried out in the
laboratory using an aluminium oxide or
silicate catalyst.
• Some unsaturated hydrocarbons are
produced because there are not enough
hydrogen atoms to give completely
saturated products.
Alcohol
• Alcohol (ethanol)
is a drug.
• If we take too
much alcohol it
can have many
harmful effects on
our bodies and
brains.
• Ethanol, for
alcoholic drinks,
can be made by
fermentation of
glucose derived
from any fruit or
vegetable.
• The type of
alcoholic drink
varies with the
plant from which
the glucose
comes.
Fermentation
• During fermentation glucose is
broken down to form ethanol;
carbon dioxide is also produced.
• Fermentation is brought about by
enzymes present in yeast.
• There is a limit to the amount of
ethanol which can be produced by
fermentation.
Distillation
• Distillation is a method of increasing
the ethanol concentration of
fermentation products in the
manufacture of ‘spirit’ drinks.
• Water and alcohols can be partially
separated by distillation because
they boil at different temperatures.
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.
H
H
H
C
C
H
H
OH
H
H
 C
C
H
H
+
H2O
• Ethanol, mixed with petrol, can be
used as a fuel for cars.
• The ethanol is obtained from sugar
cane, a renewable source of energy.
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.
• They can be recognised by the
ester link:
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
Reactions of Carbon
Compounds
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Carbon Compounds
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Plastics and
Synthetic
Fibres
Plastics and
Synthetic Fibres
• Most plastics and synthetic (i.e.
man-made) fibres are made from
materials which come from oil.
• Plastics are selected for various
uses, according to their properties
e.g. lightness, durability, electrical
and thermal insulation.
• For some purposes synthetic
materials are more suitable than
natural materials.
• Plastics are selected for various
uses, according to their properties
e.g. lightness, durability, electrical
and thermal insulation.
• There are many
examples of
plastics which we
use in our
everyday lives
•
•
•
•
•
•
•
•
•
•
Polythene
Polystyrene
Perspex
PVC
Nylon
Bakelite
Formica
Silicones
Kevlar
Poly(ethenol).
Examples of Plastics and
Synthetic Fibres
• Recently developed plastics are
• Kevlar, which is very strong
• Poly(ethenol), which readily
dissolves in water
• Synthetic fibres, like polyesters are
• Terylene
• Nylon.
Biodegradable
• Biodegradable means "able to rot
away". Most plastics are not
biodegradable and so cause
environmental problems of
disposal.
• A plastic called biopol has been
developed which is biodegradable.
Burning plastics
• Certain plastics burn or smoulder
to give poisonous fumes.
• The poisonous fumes that are
released depend on the elements
present in the plastic.
• All plastics can release carbon
monoxide.
• P.V.C. can release hydrogen chloride
• Polyurethane releases hydrogen
cyanide.
Thermoplastic or
Thermosetting?
• A thermoplastic plastic is one which can
be melted or reshaped (examples
polythene, polystyrene, P.V.C.)
• A thermosetting plastic is one which
cannot be melted and reshaped
(examples bakelite in electrical fittings,
formica in worktops)
Polymerisation
• A monomer is a small molecule which is
able to join together with other,
similar, small molecules.
• A polymer is the large molecule
produced.
• This process is called polymerisation.
• Plastics and fibres (natural and
synthetic) are examples of polymers.
The making of plastics and synthetic
fibres are examples of polymerisation.
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.
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
-CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl Repeat Unit 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.
• This repeats many times, joining
together many of the monomers
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.
• Nylon is a typical polyamide.
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
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
Plastics and Synthetic
Fibres
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Synthetic Fibres
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Natural
Products
Carbohydrates
• Carbohydrates are important
foods, produced by plants.
• Carbohydrates act as an important
source of energy for animals.
• Carbohydrates burn, releasing
energy and producing carbon
dioxide and water.
• Carbohydrates contain the
elements carbon, hydrogen and
oxygen.
• There are two hydrogen atoms for
each oxygen atom in
carbohydrates e.g. C6H12O6 and
C12H22O11
Sugars and Starch
• Carbohydrates can be divided into
sugars and starches.
Sugars
• Sugars are sweet, dissolves well in
water and let a beam of light pass
through their solutions.
• Sugars are small molecules.
• Examples of sugars include
glucose, fructose, maltose and
sucrose (table sugar).
• Monosaccharides have formula
C6H12O6.
• Disaccharides have formula
C12H22O11.
Starch
• Starch is not sweet, does not
dissolve in water and does not let a
beam of light pass through its
solution.
• Starch is a condensation polymer,
made of large molecules.
Testing Carbohydrates
• Benedict's solution (or Fehling's
solution) gives a positive test (an
orange colour) with glucose,
fructose, maltose and other sugars
but NOT sucrose.
• Iodine will turn blue/black in the
presence of starch.
Photosynthesis
• Photosynthesis is the process by
which plants make carbohydrates
and oxygen from carbon dioxide
and water, using light energy.
6CO2 +
6H2O + energy  C6H12O6 + 602
• Chlorophyll (the green colour in
plants) is used to absorb the light
energy.
Respiration
• Respiration is the process by which
animals AND plants obtain the supply of
energy that they need for growth,
movement, warmth etc.
• They obtain this energy by breaking
down the carbohydrate, glucose, using
oxygen:
C6H12O6 + 602  6CO2 + 6H20 + energy
The Atmosphere
• The combination of respiration and
photosynthesis lead to the balance of
carbon dioxide/oxygen in the
atmosphere.
• The clearing of forests with the loss of
green plants, reduces the amount of
photosynthesis taking place. This could
alter the balance of the atmosphere,
with a consequent danger to life on
Earth.
Condensation
Polymerisation
• Glucose monomers polymerise to
form starch.
• Plants convert the glucose into
starch for storing energy.
• This is a condensation
polymerisation.
nC6H12O6  (C6H10O5)n + nH2O
Hydrolysis
• Hydrolysis takes place when large
molecules are broken down into
smaller molecules by the addition
of small molecules, such as water.
• The breakdown of starch is an
example of a hydrolysis reaction.
Digestion
• During digestion starch molecules
are broken down by the body into
smaller glucose molecules that
can pass through the gut wall into
the bloodstream.
• The breakdown of starch is
brought about using acid or the
enzymes, such as amylase.
• Sucrose and starch molecules
break down by the addition of
water:
C12H22O11 + H2O  C6H12O6 + C6H12O6
sucrose
glucose fructose
(C6H10O5)n + nH2O  n C6H12O6
starch
glucose
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.
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
Proteins
• Proteins form an important class of
food made by plants.
• They are condensation polymers
made of many amino acid
molecules linked together.
• The structure of a section of
protein is based on the constituent
amino acids.
• Proteins are used to make the
main structures in animals –
muscles, tissues etc.
• They also make important
chemicals needed for the main
processes of life such as enzymes,
antibodies and hormones.
• Examples of these proteins are
insulin and haemoglobin.
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
Digestion
• During digestion enzymes
hydrolysis the proteins in our diet
to produce amino acids.
• The body then builds up the
proteins it needs from those amino
acids.
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:
This means that fat molecules fit together
easily and have a low melting point
Oil molecules do not fit together
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, usually with long
chains of carbon atoms.
• Fatty acids may be saturated or
unsaturated.
• Fats and oils are esters.
• They are made from the triol glycerol
and fatty acids.
CH2 OH
CH
OH
CH2 OH
glycerol
R C OH
O
fatty acid
• Fats and oils are esters.
• They are made from the triol glycerol
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
Natural Products
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