ALCOHOLS

• Alcohols


  Contain an -OH group and follow the general formula CnH2n+1OH
• Production of Alcohols


  1. Hydration

  2. Fermentation
• Hydration


  • Produces alcohols from alkenes in the presence of an acid catalyst
  • Phosphoric acid is commonly used as the catalyst under aqueous conditions at 300°C and high pressures
  • Has a very high percentage yield as ethanol is the only product
• Fermentation


  • Enzymes break down starch from crops into sugars which can then be fermented to form alcohol
  • Cheaper than hydration as it can be carried out at a lower temperature
  • Has to be fermented in batches, meaning it is a much slower process with a lower percentage yield
• Ethanol


  • A common biofuel produced by fermentation
  • Said to be carbon neutral as the carbon given out when it is burned is equal to the carbon taken in by the crops during the growing process
• Alcohols


  • Can be primary (1°), secondary (2°) or tertiary (3°)
  • 1° and 2° alcohols can be oxidised to produce various products but 3° alcohols are not easily oxidised
• Oxidation of Alcohols


  1. 1° alcohols can be heated in the presence of acidified potassium dichromate and distilled to produce aldehydes

  2. When heated further under reflux conditions, 1° alcohols oxidise further to produce carboxylic acids

  3. 2° alcohols can be oxidised when heated in the presence of acidified potassium dichromate to produce ketones
• Potassium Dichromate (K2Cr2O7)


  • Used in the oxidation of alcohols as the oxidising agent
  • Reduced as the alcohol is oxidised, observed as a colour change from orange to green
• Elimination Reactions


  1. Alkenes can be formed from the dehydration of alcohols, where a molecule of water is removed from the molecule

  2. Excess of hot sulfuric acid is added and aluminium oxide is used as a catalyst
• This reaction means that addition polymers can be produced from fermentation without the need for crude oil, a nonrenewable resource