6.4.2 alkenes

• Alkenes are more reactive than alkenes because they have a double carbon bond (C=C)
• Alkenes:

  • functional group: C=C
  • General formula: CnH2n
• All alkenes end in -ene
• Ethene = smallest alkene
• Alkenes are unsaturated because they contain a double bond
• Testing for alkenes - bromine water:

  • bromine water (orange) + alkene -> colourless

  Orange-brown colour will remain if an alkane is added to the bromine water.
• Alkenes and Alkanes are lighter than bromine water
• Bromine water is used to test for alkenes. The colour will change from brown -> colourless. The product is a halogenoalkane
• Hydration of ethene:

  • Ethene + water -> Ethanol
  • All reactants and products are gases.
  • Catalyst = phosphoric acid
  • High temperature = approx 300 degrees celsius
  • High pressure = approx 6500kPa