Download Organic Chemistry: Chemistry that involves Carbon

Organic Chemistry:
Chemistry that involves Carbon
Fossil Fuels: these are fuels which form from the remains of dead plants and animals
over millions of years, due to high temperatures and pressure.
Fossil fuels = Coal, Oil, (L.P.G) Gas, lignite, Peat, Diesel, Coke.
Fossil Fuels combust to release energy:
Fossil fuel + Oxygen
 Heat energy + carbon dioxide + water
Non renewable: non renewable fuels are ones that cannot be replaced within a
lifetime.
Crude Oil
Crude oil is a mixture of organic substances called HYDROCARBONS, it is a
very thick (viscous) dark brown liquid.
Hydrocarbons
A hydrocarbon is a substance which consists of Hydrogen and Carbon atoms
only.
Crude oil cannot be used in its extracted form, however once the hydrocarbon
mixture is separated it becomes many very useful substances. In order to
separate the hydrocarbon mixture a process called fraction distillation is used.
Fractional Distillation
This is a process of continuous evaporation and condensation which is used to
separate a mixture of liquids due to variations in their boiling points.
Fractional Distillation
•
•
•
•
Crude oil is split into fractions
containing similar sized molecules
using fractional distillation.
distillation.
The oil is heated until it vaporises.
It then passes up a tall tower that is
hot at the bottom but cool at the top.
As the vapour passes up this tower
the molecules cool and condense
back to liquid.
c
o
o
l
h
o
t
© Boardworks Ltd 2003
Remember this rhyme to remember the order of the fractions:
Romantic George
Preston
Never
Picks
Daffodils
For lovely
Tracey Barlow
Fraction
Refinery gas
Petrol
Naphtha
Parrafin
Diesel
Fuel oil/
Lubricating oil
Tar/bitumen
Uses
Oven gas, chemicals
vehicles
chemicals
Heating/jet engines
Vehicles diesel eng
Ship fuel, waxes,
central heating
Roofing,
waterproofing, roads
surfacing
Boiling range ◦C
-160-20
20-70
70-120
120-170
170-230
230-350
ABOVE 350
larger:
As the molecules get
1. The colour becomes increasingly yellow through to the brown/black colour of
bitumen used on roads and roof repairs.
2. They become more difficult to ignite and burn with a smokier flame.
3. The fractions become more viscous (thicker)
4. The boiling points increase.
Increasing size of molecules 
Cracking
This is an important process which converts large hydrocarbon molecules into
smaller more useful ones.
Cracking can occur by:
Thermal cracking- uses high temperatures up -1000 degrees
Catalytic cracking- uses zeolite catalysts
Large Hydrocarbon
H H H H H H H H H H
H C C C C C C C C C C H
H H H H H H H H H H
decane
Heat
pressure
H H H H H H HH
H C C C C C C CC H
H H H H H H HH
octane
catalyst
H
+
H
C C
H
H
ethene
Octane is a smaller and more useful hydrocarbon as it can be used as fuel in cars
(Petrol). This is how the worlds demand for fuels such as petrol and diesel is met, as
only a small percentage is separated from crude oil.
Homologous Series
A family of organic compounds is called a
Homologous Series.
Characteristics of a Homologous Series
have the:
 Same general formula
 Similar chemical reactivity
 Physical properties gradually change
Naming Organic Compounds the
rules:
The prefix is given according to the
number of carbon atoms present in
the chain.
No. of Carbons
Prefix
1 Carbon atom
2 Carbon atoms
3 Carbon atoms
4 Carbon atoms
5 Carbon atoms
6 Carbon atoms
MethEthPropButPentHex-
1. The Alkanes
Alkanes are the first family of organic
chemicals and have very similar structures.
They all contain
C – C single bonds
C – H single bonds
*All Carbon atoms MUST be surrounded by 4
bonds*
The Alkanes all have the general formula of
CnH2n+2
They are said to be saturated which means
they contain only
C-C single bonds.
H
methane, CH4
H
C
H
H
H
H
ethane, C2H6
H
C
C
H
H
Try drawing the next 4 members!
H
H
H
H
H
C
C
C
H
H
H
propane, C3H8
H
butane, C4H10
H
H
H
H
H
C
C
C
C
H
H
H
H
H
pentane, C5H12
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
hexane, C6H14
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
Combustion of Alkanes
Why are alkanes used as fuels?
Combustion in the presence of Oxygen
Carbon Dioxide and water is formed !
Methane + oxygen  water + carbon
dioxide
CH4 + O2
 H2O +
CO2
Balance Equation !
L.H.S
=
R.H.S
C=
H=
O=
Task: Write out the balanced equations for the combustion of Ethane
Propane and Butane, assuming Oxygen is present.
H
Combustion in the limited supply of Oxygen
Methane + oxygen  water
2CH4 + 3O2

+ carbon monoxide
4H2O
+
2CO
• Carbon monoxide is highly poisonous and this is one reason why
gas boilers must be serviced regularly.
2. The Alkenes
Remember all C atoms are surrounded by 4 bonds. This does not,
however, mean that each carbon is joined to four other atoms.
It is possible to have bonds grouped into pairs. These are called double
bonds.
Alkenes contain carbon atoms joined by one double covalent bond C=C
Alkenes have the general formula CnH2n
• The 1st Member = The simplest alkene is ethene.
It has the formula C2H4
H
H
C
C
H
H
H
or
H
C
C
H
H
Alkenes are said to be unsaturated, which means they contain a carbon,
carbon double bond C=C. They are also considered HYDROCARBONS.
Alkenes are reactive hydrocarbons due to the presence of the C=C bonds
which can be broken.
They also burn in Oxygen to form Carbon dioxide, water and liberate
energy.
Task: Draw the structural formula for: Propene, butene and pentene.
Reactions of Alkenes
Alkenes are unsaturated and so extra atoms can be
added to alkene molecules.
The 3 Alkene reactions we will learn about are:
1. Addition of Bromine
2. Addition of Hydrogen
3. Addition of Water
1. Addition of Bromine
•
This forms the basis of a test to distinguish between
alkanes and alkenes.
•
When bromine water is added to an alkane nothing happens! but when
When
is added
to anofalkane
nothing
bromine
waterbromine
is added towater
an alkene
the red colour
the bromine
happens
but when bromine
decolourises.
1,2-dibromoethane
forms is added to an alkene
the red colour of the bromine disappears.
Bromine
loses this
red colour
H
H
C
Gas
C
H
H
+
Br2
red

Br Br
H C C H
H H
colourless
2. Addition of Hydrogen
H
H
C
C
H
+
H-H

H
3. Addition of water (Hydration of Ethene)
H
H
C
C
H
+
H20 
H
Ethene
+
Steam 
Ethanol
This is an ADDITION REACTION, ethene is hydrated with the
following conditions: A phosphoric acid catalyst,
Temperature of 330 ◦C
Pressure = 70 atm
Addition Polymerisation reactions
Addition polymerisation is the joining together of many small molecules
called monomers, by the breaking of the C=C bonds to from long chain
molecules called polymers.
H
n
H
C
C
H
H
ethene
Pressure
high
temperature
catalyst
H H
C C
H H n
polythene
n = 500- 1000 units
Use you text book page 176 to draw out other polymers and list their
properties and uses.
Alcohols
Alcohols are a group of organic compounds that contain an ‘OH’ group
The general formula for alcohols = CnH2n+1.OH
H
methanol, CH3OH
C
H
H
H
0H
H
H
H
C
C
H
H
Ethanol, C2H5OH
OH
Alcohols are formed from the Fermentation of Glucose.
Glucose
Yeast

Ethanol + Carbon dioxide
Enzymes
The following conditions are required:
 Glucose
 A controlled temperature
 Yeast
 No oxygen present
Questions:
1. Why does the temperature have to be controlled in the above
reaction?
2. Why is alcohol added to petrol in countries such as Brazil?
3. List the uses of Ethanol
Alcohols burn in oxygen forming carbon dioxide and water.
Ethanol + Oxygen  Energy + carbon dioxide + water
Task : complete the symbol equation!
Carboxylic acids
Carboxylic acids contain a COOH group.
Ethanoic acid
H
CH3COOH
H
O
C
C
H
H
O-H
Carboxylic acids are weak acid. Ethanoic acid has a strong characteristic
smell like vinegar. It is a colourless liquid.
These organic acids react like mineral acids such as hydrochloric or
sulphuric acid.
Remember the following equations! :
Metal + Acid  Salt + Hydrogen
Acid + Metal Oxide (base)  Salt + water
Acid + carbonate  Salt + water +carbon dioxide
Acid + alkali  Salt + water.
The salts formed from Ethanoic acid end in ‘Ethanoate’
Eg
Sodium + ethanoic acid  Sodium ethanoate + Hydrogen
Complete the following:
1. Magnesium + ethanoic acid
2. Zinc oxide + ethanoic acid
3. Sodium carbonate + ethanoic acid
4. Potassium + ethanoic acid
5. Copper oxide + ethanoic acid
6. Copper carbonate + ethanoic acid
Esterification
Esters are formed when alcohols react with carboxylic acids.
Esters are liquids with a sweet smell. They are used in solvents such
as glue and flavourings.
How esters form
In the lab we can prepare the ester Ethyl Ethanoate by gently heating
together Ethanol and Ethanoic acid in the presence of conc sulphuric
acid (Catalyst).
Ethanoic acid +
Ethanol

Ethyl Ethanoate