Transcript 3abc NEW Alkanes alkenes ethanol 5b and c Natural oil gas and

Topics 3abc – Alkanes, alkenes
and ethanol
Topics 5bc – natural oil and gas
and synthetic polymers
Crude oil (Petroleum)
• A mixture of hydrocarbons (chemicals
which contain only hydrogen and carbon
atoms)
Fractional distillation
• Separation of
liquids with
different boiling
points
Fractional distillation
The mixture can be split into simpler
fractions by fractional distillation
Welcome to a new family
The alkanes
Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10)
The alkanes
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Methane
Ethane
Propane
Butane
Pentane
Hexane
Octane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C8H18
General
formula
The alkanes CnH2n + 2
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Methane
Ethane
Propane
Butane
Pentane
Hexane
Octane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C8H18
Homologous group –
similar chemical
properties, structures
and functional
groups
General
formula
The alkanes CnH2n + 2
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Methane
Ethane
Propane
Butane
Pentane
Hexane
Octane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C8H18
Homologous group –
similar chemical
properties, structures
and functional
groups
Generally unreactive,
but burn exothermically.
Longer chains burn less
easily.
Structural formulae
Alkanes are saturated compounds
No double
bonds
Tetrahedral bonds
In alkanes, the carbon bonds are tetrahedral
Chlorinated methane
Methane can be chlorinated.
Trichloromethane is commonly known as
chloroform.
Isomers
Same formula, but different structures
We have slighty different physical
properties (longer chains have
higher boiling points)
Combustion
Combustion
Hydrocarbons burn producing carbon
dioxide and water
CH4 + 2O2
CO2 + 2H2O
Incomplete combustion
• When there is
insufficient
oxygen, carbon
monoxide is also
formed
It reduces the blood’s oxygen
carrying capability
Another family!
The alkenes CnH2n
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Ethene C2H4
Propene C3H6
Butene C4H8
Pentene C5H10
Hexene C6H12
The alkenes
• Unsaturated (contain a double bond)
• More reactive
• Can “add” atoms – addition reactions
Alkenes - equilateral
The bonds on a double bonded carbon in an
alkene point towards the corners of an
equilateral triangle
Test for alkenes
• Decolourises bromine water
ethene
Bromine
(yellow/orange)
Dibromoethane
(colourless)
Alcohols - ethanol
Alcohols
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Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH
Alcohols
“functional group”
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Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH
Ethanol
Can be made by the addition reaction of
water to ethene – when you have plenty of
oil
Phosphoric acid
Ethanol - Fermentation of sugars
You can make ethanol for
industry this way when you have
lots of sugar cane
Dehydration of Ethanol
Ethanol and sodium
2C2H5OH + 2Na
2C2H5ONa + H2
Hydrogen and sodium ethoxide formed
Oxidation of ethanol
Ethanol can be
oxidised to form
ethanoic acid
(acetic acid =
vinegar!)
Carboxylic acids
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Methanoic acid CHOOH
Ethanoic acid C2H3OOH
Propanoic acid C3H5OOH
Butanoic acid C4H7OOH
Pentanoic acid C5H9OOH
Hexanoic acid C6H11OOH
Carboxylic acids
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Methanoic acid CHOOH
Ethanoic acid C2H3OOH
Propanoic acid C3H5OOH
Butanoic acid C4H7OOH
Pentanoic acid C5H9OOH
Hexanoic acid C6H11OOH
“functional group”
Ethanol + ethanoic acid acids
Ethanol + ethanoic acid
ethyl ethanoate + water
An ester (they normally
smell nice!)
Ethyl ethanoate – an “ester”
Polymers
Polymers – addition polymerisation
Molecules of ethene can be joined together
to form polyethene
← monomers
← polymer
Polythene
Polypropylene – Strong and
resistant to chemicals
poly(chloroethene) - PVC
Condensation polymers – Nylon
Diamine + dicarboxylic acid
Reactive ends
+
+
+
monomers
polymer
Small molecules given off (HCl)
Cracking!
Too many long molecules
Crude oil contains too many of the long
(and not so useful molecules)
Cracking
Luckily we can break the long molecules into
shorter ones by “cracking”
The long molecules are passed over hot broken pot
(ceramic) and split up into smaller molecules. A
catalyst can also be used
Cracking
Cracking an alkane produces smaller
alkanes and also alkenes.