Alkane is a saturated hydrocarbon due to the carbon carbon single bond.
Alkane is generally unreactivity, however it undergoes 3 reactions.
1. Combustion
Alkane + oxygen —> carbon dioxide + steam
Alkanes are used as fuel they
burn readily in the air with a blue
non-sooty flame to release a lot of heat and energy.
2. Cracking the process by which long chain hydrocarbons are broken into smaller more
useful hydrocarbons .
● Thermal cracking process by which high temperature above 900 degree Celsius is
used to break long chain hydrocarbons are broken into smaller more useful
hydrocarbons.
● Catalytic cracking the process by which a catalyst and temperature of about 450 degree
Celsius is used to break long chain hydrocarbons are broken into smaller more useful
fractions.
In cracking make sure:
● The number of carbon on the left is equal to the total number of carbon on the right.
● the number of hydrogen on the left is equal to the total number of Hydrogen on the right.
Importance of cracking
Produce usually alkane such as gasoline
Produces reactive Alkene needed in the petrochemical industry.
.
3. Substitution reaction.
In a substitution reaction one hydrogen from the alkane is replaced by a halogen atom and an
organic product is formed and hydrogen halide. The organic product form reacts with a new
halogen molecule each time until the substitution is completed.
Testing for hydrogen chloride place a glass rod dipped in concentrated ammonia dense white
fumes would be seen produce if hydrogen chloride is present.
Uses of alkane
1. Methane (CH4):
○ Natural gas (used for heating, cooking, and electricity generation)
○ Feedstock for the production of hydrogen and synthesis gas
○ Raw material in the chemical industry for the production of various organic
compounds
2. Ethane (C2H6):
○ Feedstock for the production of ethylene, a primary raw material for
plastics manufacturing
○ Used as a refrigerant and as fuel for engines and heating
3. Propane (C3H8):
○ Liquefied petroleum gas (LPG) for heating, cooking, and fueling vehicles
○ Feedstock for the production of propylene, used in the manufacture of
plastics, synthetic fibers, and other chemicals
4. Butane (C4H10):
○ LPG component for domestic and industrial use
○ Fuel for lighters and camping stoves
○ Feedstock for the production of butadiene, used in the production of
synthetic rubber
5. Pentane (C5H12):
○ Component in gasoline blends, especially in cold weather to improve
volatility
○ Used as a blowing agent in the production of foam insulation and
packaging materials
6. Hexane (C6H14):
○ Solvent for extracting oil from seeds and vegetables
○ Cleaning agent in the printing industry
○ Used as a carrier solvent in the manufacture of glues, varnishes, and
adhesives
Alkene
Unsaturated hydrocarbon due to carbon carbon double bond.
Reaction
Combustion burns and produces a sooty or Smokey flame and gives carbon dioxide and steam
Addition reaction of Alkene.
When Alkene reacts the double is converted to a single and atom/s is added to each carbon that
where in the double bond.
1. Hydrogenation (addition of 2 H atoms across the double bonds).
Alkene and hydrogen gas react using nickel catalyst and 1500C to produce alkene.
2. Halogenation (addition of 2 X atoms or a H and X atom across the double bonds).
✔ Alkene and halogens produces dihaloalkanes.
Note: Alkene can react in the dark with halogen unlike alkane.
✔ Alkenes and hydrogen halide produces haloalkanes
3. Hydration (addition of H and OH atoms across the double bond).
Alkene and steam in the presence of produces alcohol.
4. Oxidation with acidified potassium permanganate (addition of OH and OH across
the double bond). The purple potassium permanganate solution is decolourised by
alkene.
H2C=CH2 + [O] + H2O (l) ======> HO-CH2-CH2OH (ethane -1,2, diol
Reagent Alkane Alkene
Bromine liquid Bromine remains red/red- Brpomine turns from
brown red/redbrown to colourless
Bromine solution Orange bromine water remain Orange bromine water will
orange turn colourless
Bromine liquid in uv light Bromine red colour slowly Bromine rapidly changes from
changes to colourless red to colourless.
Acidified potassium KMnO4 remains purple KMnO4 remains purple to
manganate (VII) colourless
DISTINGUISH BETWEEN ALKANE AND ALKENE
