Alkanes Flashcards
Petroleum
A mixture of mainly alkane hydrocarbons separated by fractional distillation
What are Alkanes? What are they used for?
Saturated hydrocarbons containing C-H bonds only
Main constituent of crude oil
Used as Fuel
Alkane General Formula
CnH2n+2
Alkane Bond Polarity?
Non-Polar as C and H have similar electronegativities
Alkane Intermolecular Forces?
Only van der Waals forces of attraction - bonds are non-polar
Alkane Solubility?
Insoluble because hydrogen bonds in water are stronger than alkanes’ van der Waals forces of attraction
Alkane Reactivity?
Very unreactive
Fractional Distillation Process
Crude oil heated until mostly vapourised
Passed into a fractionating tower that is cooler at the top than the bottom
Liquid fractions are piped off at the bottom
Vapours rise up the column and condense when temperature < their boiling point
Shortest chain hydrocarbons condense at the top as they have the lowest boiling points
What is cracking?
Breaking the C-C bond
Thermal Vs Catalytic Cracking
Thermal:
1200K - 7000 kPa
Makes alkenes
Catalytic:
720k - Slight Pressure - Zeolite catalyst
Makes: Cycloalkanes, aromatic hydrocarbons, branched alkanes
What are alkanes used for?
Fuels
How do alkanes combust?
Completely or Incompletely
Internal Combustion Engine Pollutants
NOX, CO, Unburned Hydrocarbons
Can be removed by catalytic coverters
Flue gas desulphurisation
Removes sulphur dioxide from the air using CaO
CaO + SO2 +2H2O + 1/2 O2–> CaSO4.2H20
CaCO3 + ½O2 + SO2 → CaSO4 + CO2
Chlorination of Alkanes
Free radical substitution mechanism
