C7 - Organic Chemistry

• Hydrocarbons contain only hydrogen and carbon atoms
• Alkanes:

  • Only single carbon bonds
  • General forCnH2n+2
  • They are a homologous series - group of organic compounds that react similarly
  • Saturated with carbon
  • First four are

  1. Methane
  2. Ethane
  3. Propane
  4. Butane
• Shorter hydrocarbon chain:

  • Less viscous
  • More volatile
  • More flammable
  • Lower boiling points
• Complete combustion:

  • When there is sufficient oxygen
  • In hydrocarbons, it produces CO2 and water
  • Both the carbon and hydrogen are oxidised
  • Incomplete combustion produces CO and H
• Crude oil:

  • Made of buried remains of plants and animals
  • Over millions of years with high temperature and pressure they turn into crude oil
• Fractional distillation:

  • Oil evaporated and enters fractionating column
  • Temperature gradient hottest at the bottom
  • Long hydrocarbons have higher boiling points and condense and are collected lower in the column
  • Crude oil ends up separated into different fractions
• Crude oil fractions are used for:

  • Polymers
  • Solvents
  • Lubricants
  • Detergents
• Cracking:

  • Steam cracking uses higher temperature and pressure
  • Catalytic cracking uses a catalyst with lower temperature and pressure
• Cracking is breaking down long-chain alkanes into short-chain alkanes and alkenes
• Bromine water test:

  • Alkane - it stays orange
  • Alkene - it changes to colourless