Organic Chemistry
Organic chemistry is a sub-discipline in
chemistry that involves the scientific study of
the structure, properties and reactions of
organic materials and compounds.
Meeting the Alkanes
The alkanes are hydrocarbons, containing only
hydrogen and carbon
The Alkanes
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Why do we
use alkanes?
Burning alkanes
If there is plenty of air, ie enough oxygen:
Methane + Oxygen  Carbon dioxide + Water
you
write
the
balanced
symbol
CHCan
+
2O

CO
+ 2H20(g)
4(g)
2(g)
2(g)
equation?
Did you remember state
symbols?
Alkanes and Aqueous Reagents
Alkanes are unreactive towards aqueous
reagents because they contain only C—C and
C—H bonds, which are difficult to break and
therefore unreactive
H H H
H C
C
C H
H H H
Functional Groups
All of the characteristic properties
of alcohols are due to the presence
of this functional
H H group.
H C
C H
O H
Can you give the molecular formula, structural
formula,
stick diagram for methanol and
H H
ethanol?
Ethanol
Ethane
Why do we need
methanol and
ethanol?
Uses of alcohols
Methanol
Ethanol
C2H5OH
CH3OH
Chemical feedstock
Fuel
Manufacture of cosmetics
Solvent
Burning Alcohols in Air
1. Can you write out the word equation for the combustion of
ethanol in air.
2. Write out the balanced symbol equation
3. Don’t forget state symbols
Ethanol + Oxygen  Water + Carbon dioxide
C2H5OH (l) +
3O2(g)
3H20(g) +
2CO2(g)
Alcohols burn in air to produce carbon dioxide and water
because of the presence of a hydrocarbon chain
Why have I been
using methanol
and ethanol for the
demonstrations?
Physical Properties
The longer the hydrocarbon the
stronger the intermolecular forces and
therefore the higher the boiling point.
Longer hydrocarbons are also less
soluble in water as they behave more
like an alkane and so float on top of
water due to their low density
Reactions with Sodium
Remember this?
Sodium with water
Alcohols- Sodium sinks in alcohol and
doesn’t melt, it will steadily give off
hydrogen
Sodium with alcohol
Alkanes- Do not react with Sodium
Quick Quiz so far
1.
2.
3.
4.
5.
Draw the structural formula for butanol
Write the molecular formula for butanol
Draw the structural formula for hexane
Write the molecular formula for hexane
Write the molecular formula for an alkane with
25 carbon atoms.
6. How many bonds does oxygen make in
methanol?
7. Give an example of a use for ethanol
8. Give an example of a use for methanol
1.
2.
3.
4.
5.
6.
7.
Butanol
C4H10O
Hexane
C6H14
C25H52
2
Fuel/feedstock for synthesis/solvent/used in
perfume
8. Solvent, antifreeze, feedstock for adhesives
and plastics
How do we make ethanol?
• What process do we use? It will be used in
home brewing
• Fermentation is a key process for obtaining
ethanol. It is relatively cheap and requires
wheat or beet sugar.
• The process involves the anaerobic respiration
of yeast at temperatures between 20 and 40°C
and at pH 7.
Why is there a limit
on the strength of
alcohol that can be
made?
Key
Making Alcohol
Sugar
Ethanol
When the ethanol
concentration
gets too high it
kills off the yeast
cells
So how do we
make stronger
alcohol?
How do we obtain a concentrated
solution?
• Ethanol has a different boiling point to water.
We can therefore separate water and ethanol
using distillation.
Give it a thought
Can you balance this equation?
C6H12O6 → 2 CH3CH2OH+ 2 CO2
Can you
name the
chemicals?
Other ways to make ethanol
Genetically modified E. coli bacteria can be used
to convert waste biomass from a range of
sources into ethanol
Optimum conditions:
Temperature remain
between 25-37oC
Optimum pH level needs
to remain constant
Other ways to make ethanol
They introduce new genes into the E.coli
bacteria allowing it to digest all the sugars in
the biomass and covert them into ethanol.
Therefore we can use a wide range of biomass
to make ethanol rather than staying as waste
eg corn stalks.
Feedstock
Linking alkanes and alcohol
Crude Oil undergoes fractional distillation
Long chain hydrocarbons (alkanes) are vaporised
then cracked using a catalyst and heat
The molecules are purified using fractional
distillation producing ethene
Ethene is then reacted with steam, at a high
temperature and with a catalyst to produce ethanol
Any unreacted products can
be recycled and fed through
the system again
It is also possible to convert ethane into ethanol
Write out the Symbol Equation
Ethene + Steam  Ethanol
C2H4 (g)+ H20(g) C2H5OH(g)
The UK is the world's largest producer
of synthetic ethanol
Why is this
not a good
fact?
4.
Make a table listing the advantages and disadvantages of each
method of producing ethanol.
Advantage
Disadvantage
Fermentation
renewable feedstocks,
which include waste
materials
maximum concentration
of ethanol 15%
Biotechnology
uses feedstocks that
cannot be used in
traditional fermentation,
reducing waste; produces
higher concentrations of
ethanol
new technology still in
development
Chemical
synthesis
production of high
concentrations of ethanol;
100% atom economy and
high yields
feedstock non-renewable
Tackling the 6 marker
Which method do you think has the largest
impact on the environment? Give reasons for
your answer.
The Alkanes
H
H C H
H H H
H C
C
C H
H
H H H
H H
H H H H
H C
C H H C C C C H
H H
H H H H
H H H H H H H H
H C C C C C C C C O
H H
H H H H H H H
H C O H
H H
H
H C
C O H
H H