Download Sources of Hydrocarbons 5.1

Sources of
Hydrocarbons
Hydrocarbons
Hydrocarbons
are
compounds consisting
of hydrogen and
carbon only, bonded
together covalently.
Sources
Fossil Fuels
Crude Oil
Natural gas
Coal

Crude oil and natural gas were formed from
the remains of marine plants and animals.

Coal was produced from dead wood
Hydrocarbons
CH4
Methane
Methane Production
Methane can be produced in:
 Coalmines
 Slurry pits
 Waste dumps
 Digestive tracts of animals
Hazards of Methane Production



Fires and explosions
Death by suffocation
Contributes to the greenhouse effect
When the chain is between 5 and 9 carbons, the hydrocarbon is gasoline. About a dozen carbons and it is
diesel. Around 20 carbons is motor oil. A chain of hundreds to thousands of carbon and hydrogens make
plastic. This particular plastic is polyethylene.
Petroleum distillation
Carbon groups
•
•
•
•
•
•
•
Alkanes
Methane
Ethane
Propane
Butane
Pentane
Hexane
CnH2n+2
CH4 GAS
C2H6 GAS
C3H8 GAS
C4H10 GAS
C5H12 LIQUID
C6H14 LIQUID
Naming carbon groups
•
•
•
•
•
Methyl
Ethyl
Propyl
Butyl
Pentyl
CH3
C2H5
C3H7
C4H9
C5H11
Alkanes
• Hydrocarbon chains where all the bonds
between carbons are SINGLE bonds
• Name uses the ending –ane
• Examples: Methane, Propane, Butane,
Octane, 2-methylpentane
Step 1. Find the parent chain.
• Where is the longest continuous chain of
carbons?
Step 2. Number the parent chain.
• Number the parent chain so that the
attached groups are on the lowest
numbers
Methyl is on carbon #2 of the parent chain
Methyl is on carbon #4 of the parent chain
1
5
1 8
2
4
3
3
4
2
3 6
7 2
8 1
4 5 5 4
6 3
5
1
GREEN is the right
way for this one!
27
1
7
2
6
3
5
4
4
Groups on 2 and 5
Groups on 4, 6, and 7
Groups on 2, 3, and 5
5
3
6
72
1
Groups on 3 and 6
Step 3. Name the attached groups.
• Carbon (alkyl) groups
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
• Halogens
– Fluoro (F-)
– Chloro (Cl-)
– Bromo (Br-)
– Iodo (I-)
Step 4. Designate where the group
is attached to the parent chain.
• Use the numbers of the parent chain from
step 2 to designate the location of the
attached groups to the parent chain.
2-methyl
1
2
3
4
5
Step 5. Alphabetize the groups,
combine like groups, and assemble.
• The prefixes di, tri, tetra
etc., used to designate
several groups of the
same kind
• Prefixes are not
considered when
alphabetizing (Example:
dimethyl = m for
alphabetizing)
• Parent chain goes LAST
1,1,1-trichloro-1fluoromethane
1,1-dichloro-1,1difluoromethane
Draw Some Simple Alkanes
• 2-methylpentane
• 3-ethylhexane
• 2,2-dimethylbutane
• 2,3-dimethylbutane
Alkenes
•
•
•
•
•
•
CnH2n-2
Ethene
Propene
Butene
Pentene
Hexene
Alkenes
Preparation and properties of
Ethene gas
Aluminium oxide(CATALYST) removes a
water molecule from ethanol and produces
ethene gas
Preparation of ethene
Practical precautions of ethene
• Avoid suck back by
removing heat
before dismantling
the equipment
• Discard first gas jar
as it will have a mix
of air and ethene
Precautions
•
•
•
Why is it desirable to push the glass wool into
the tube after the ethanol has been added?
To ensure that all of the ethanol is soaked up.
Why should the ethanol not be heated strongly?
Strong heating of the ethanol will cause it to
evaporate too quickly and escape from the tube
before it can be dehydrated.
PHYSICAL PROPERTIES: It is a colourless gas with a sweetish
smell. It is insoluble in water so you can collect it over water.
COMBUSTION
C₂H₄ + 3O₂ → 2CO₂ + 2H₂O
LIME WATER TEST
Ethyne preparation
Preparation of ethyne
• The first test tube
should be
discarded.
• Add small amounts
of calcium carbide
as it is very reactive
with water
TOLLENS REAGENT TEST FOR ALDEHYDES
Aldehydes and ketones behave differently.
You will remember that the difference between an
aldehyde and a ketone is the presence of a hydrogen
atom attached to the carbon-oxygen double bond in
the aldehyde. Ketones don't have that hydrogen.
Fehlings test is used to distinguish the diffference in
functional groups.