C7 - Organic Chemistry

• Crude Oil

  • A form of oil found in rocks and is made from the remains of dead biomass buried in mud; however, it's a finite resource
• Hydrocarbons

  • Most of the compounds in crude oil are known as hydrocarbons -> Molecules made of Hydrogen + Carbon ONLY
• What is the general formula for alkanes?

  $CnH2n+$$2$
• What are the 4 members of the alkanes known as?

  • Methane
  • Ethane
  • Propane
  • Butane
• Alkanes

  • Hydrocarbons found in crude oil
• How do we separate crude oil?

  • Fractional Distillation
• Explain Fractional Distillation

  • Fractional distillation is the process of separating the different hydrocarbon compounds within crude oil
  • Firstly, the crude oil is heated and fed into the fractionating column which has a temperature gradient, meaning that it's hotter at the bottom and cooler at the top
  • Long chain hydrocarbons with a higher BP will condense at the bottom of the column, whilst shorter chain hydrocarbons with lower BP will rise up and condense at the top of the column
• Combustion

  • A term for BURNING
• Hydrocarbon fuels release what during combustion...?

  • Energy
• Complete Combustion

  • Fuel + Oxygen -> Carbon Dioxide + Water
• What occurs during combustion?

  • Carbon + Hydrogen in the fuels are oxidised (reacts with oxygen) to produce Carbon Dioxide + Water
• Properties of hydrocarbons can be influenced by...

  • The length of the carbon chain
• 3 Properties that are affected in hydrocarbons (due to the length of the carbon chain) :

  • Boiling Points
  • Viscosity
  • Flammability
• Properties of short chain hydrocarbons

  • Highly Flammable + have a Low BP
  • Lower Viscosity (Tend to flow more quickly)
• Properties of long chain hydrocarbons

  • Less Flammable + have a High BP
  • Higher Viscosity (Tend to flow more slowly)
• Methane

  -> CH(4)

  
• Ethane 


  -> C(2)H(6)

  
• Propane


  -> C(3)H(8)

  
• Butane


  -> C(4)H(10)

  
• Petrochemical

  • Fractions can be processed to produce fuels and feed stock for the petrochemical industry

  -> Materials produced by the petrochemical industry include:

  • Polymers
  • Solvents
  • Lubricants
  • Detergents
• Cracking

  • Thermal Decomposition of large hydrocarbons into smaller + more useful hydrocarbons
• Why must long chain hydrocarbons be cracked?

  • Long-chain hydrocarbons do not make good fuels as they aren't very flammable.
  • However, short-chain hydrocarbons are in high demand to be used as fuel.
  • Therefore, we must convert long-chain hydrocarbons into shorter-chain hydrocarbons via cracking.
• What are the 2 products of cracking?

  • Alkanes + Alkenes
• What are the 2 types of cracking?

  • Catalytic Cracking
  • Steam Cracking
• Catalytic Cracking

  1. Heat the long-chain hydrocarbons to vaporise them
  2. This vapour is passed over a hot catalyst e.g. Aluminium Oxide
  3. As the long-chain hydrocarbons come into contact with the catalyst, it splits apart to form a short-chain alkane + alkene
• Steam Cracking

  1. Heat the long-chain hydrocarbons to vaporise them
  2. Mix this vapour with steam
  3. Heat this mixture to a very high temperature
  4. The long-chain hydrocarbons split apart to form a short-chain alkane + alkene
• 2 Properties of alkenes

  • More reactive than alkanes
  • Double covalent bonds
• How do we test for the presence of alkenes?

  • By adding bromine water to an alkene; the solution will turn from orange -> colourless
• What can alkenes be used for ?

  • Alkenes can be added together to form polymers
  • OR as starting materials for the production of many other chemicals
• What are the 2 conditions required for cracking?

  • High Temperatures
  • High Pressure
• Incomplete Combustion

  Fuel + Oxygen -> Carbon Monoxide/Carbon + Water
• Are alkenes saturated or unsaturated?

  • Unsaturated
• Are alkanes saturated or unsaturated?

  • Saturated
• Why isn't crude oil a formulation?

  • Isn't designed as a useful product
  • Isn't the same composition all the time