alkenes

• reaction

  + hydrogen -> alkanes

  addition
• reaction

  + halogens -> dihaloalkanes

  addition
• reaction

  + hydrogen halides -> monohaloalkanes

  addition
• reaction

  + water -> alcohols

  addition
• preparation

  alcohol vapour + hot aluminium oxide

  elimination (dehydration of alcohols)
• preparation

  alcohol + concentrated sulfuric or phosphoric acid

  elimination (dehydration of alcohols)
• preparation

  monohaloalkane + ethanolic potassium or sodium hydroxide

  elimination (base-induced elimination of hydrogen-halides from monohaloalkanes)