topic c7- organic chemistry

• hydrocarbons

  any compound formed by hydrogen and carbon only
• alkanes

  • general formula- CnH2n+2
  • saturated compounds- each C has 4 bonds
  • a homologous series- a group that react in a similar way
• methane

  CH4

  
• ethane

  C2H6

  
• propane

  C3H8

  
• short hydrocarbon chain properties

  • more viscous- more runny
  • more volatile- lower boiling point
  • more flammable
  • burns with clean flame

  long chains are the opposite <----->
• fractional distillation

  
• fractional distillation

  • top- cool
  • liquified petroleum gas
  • petrol
  • kerosene
  • diesel oil
  • heavy fuel oil
  • bottom- very hot
• fractional distillation

  • crude oil is entered into the bottom of the fractionating column
  • it is very hot at the bottom and cools as it goes up
  • longer chains have higher boiling points, so condense earlier
  • as the chains get shorter, the boiling points get lower
  • this separates all the hydrocarbons inside the crude oil into useful substances
• cracking

  • as mentioned previously, short chains of hydrocarbons have more desirable traits compared to long chains
  • the cracking of alkanes effectively snaps a long alkane chain into a shorter alkane and alkene
• cracking

  
• alkenes

  • general formula- CnH2n
  • unsaturated compounds- contains C=C double bonds
  • a homologous series- a group that react in a similar way
• ethene

  C2H4

  
• propene

  C3H6