Elimination Reaction of Alcohols

• Alcohols can also undergo?dehydration?to form alkenes
  • This is an example of an elimination reaction
  • Elimination reactions involve a small molecule leaving the parent molecule as a byproduct
  • In this case, the small molecule is a water molecule
  • The water molecule is formed from the -OH group and a hydrogen atom from the adjacent carbon atom

   

• Alcohol vapour is passed over a?hot catalyst?of aluminium oxide (Al2O3) powder or pieces of porous pot
  • Excess hot, concentrated sulfuric acid or phosphoric acid is used as a catalyst

   

Dehydration of ethanol using aluminium oxide as a catalyst forms ethene gas, which can be collected over water

• The reaction and mechanism for the dehydration of propan-1-ol is shown below

Dehydration of propan-1-ol mechanism