13.3 Reactions of alkenes

• Alkenes undergo addition reactions when a small molecule is added to the double bond, breaking the pi bond
• Alkenes react with hydrogen in the presence of a nickel catalyst to form alkanes
• Alkenes react with halogens to form halogenoalkanes
• Unsaturated hydrocarbons decolourise bromine water

  • orange bromine water is added to an excess of an organic compound and shake the mixture
  • bromine adds to the double bond forming a colourless product
  • if the compound is saturated, no colour change occurs
• Alkenes react with steam to form alcohols