Alcohols

• Alcohols


  • organic compounds that contain hydroxyl (-OH) functional group
  • General formula CnH(2n+1)OH
• Physical Properties of alcohols

  • boiling point increases down homologous series, intermolecular forces of attraction increase as molecular size of alcohols increases, thus more energy required to overcome intermolecular forces of attraction
  • Solubility decreases as relative molecular mass increases
  • Alcohols are not alkalis!!
• Chemical properties of alcohols

  • Undergo complete combustion by burning in excess oxygen to form carbon dioxide and water
  • burn with clean blue flame without soot as percentage by mass of carbon in them is lower compared to alkane and alkene
  • alcohols with hydroxyl group bonded to carbon atom at end of their carbon chain are oxidised to carboxylic acids when they are heated with oxidising agents (e.g. acidified potassium manganate (VII))
• Formation of ethanol (Hydration)


  • addition of steam to ethene (Hydration)
  • Ethene reacts with steam at 300 degree celcius and 60 atm in the presence of phosphoric(V) acid (H3PO4) catalyst to form ethanol
• Formation of ethanol (fermentation)


  • ethanol can be produced by fermentation of glucose in fruits, vegetables or grains
  • During fermentation, yeast acts on glucose in the absence of oxygen to form ethanol and carbon dioxide
  • High temperatures cause the enzymes in yeast to denature and fermentation to stop
  • Fermentation takes longer than hydration but is a more sustainable method of producing ethanol as starting materials are obtained from renewable resources (e.g. sugarcane)