organic chemistry

• Crude oil is a mixture of hydrocarbons, which are long chains of hydrogen and carbon atoms.
• alkanes are saturated hydrocarbons, they contain C-C and C-H bonds only, they are apart of the same homologous series as they have the same general formula and properties
• Alkanes follow the general formula CnH2n+2
• Properties of long chain hydrocarbons -

  • high viscosity
• properties of long chain hydrocarbons -

  • high viscosity
  • low volatility
  • low flammability
  • high boiling point
• properties of short chain hydrocarbons -

  • low viscosity
  • high volatility
  • high flammability
  • low boiling point
• HydroCarbons can be broken down (cracked) to produce smaller, more useful molecules
• Catalytic cracking - cheaper

  • Zeolite catalyst (contains Aluminium Oxide)
  • Temperature of 500 degrees Centigrade
• Steam cracking

  • no catalyst
  • higher temperature (750 degrees Centigrade)
• when cracking occurs a long chain alkane is thermally decomposed into a mixture of shorter alkanes and alkenes
• alkenes are unsaturated as they contain a C=C bond
• Polymers (plastics) - long molecules of repeating monomers (small molecules)
• Fractional distillation

  • heat crude oil to a vapour
  • vapours enter column at the bottom and separate by boiling point
  • the column is coolest at the top, and hottest at the bottom
  • fractions (hydrocarbons) condense at different temperatures
  • shorter fractions condense towards the top due to their lower boiling point

  
• Alkene + Bromine turns colourless, Alkenes react with Bromine because of their double Carbon bond
• Alkane + Bromine stays orange