Alcohols

• Hydroxyl (OH) group


  Functional group of alcohols
• Alcohol names


  End in '-anol' (i.e. heptan-3-ol)
• Alcohols tend to have neutral pH's
• Alcohols are not hydrocarbons - they have oxygen
• Uses of alcohols


  • Solvent
  • Biofuel
  • Sterilisation
  • Production of esters
  • Alcoholic drinks
• Number of carbons in alcohols

  Boiling point increases as number of carbons increases
• Diol


  Two OH groups
• Naming diols


  Give the alkane name (i.e. propane), then the position of the two groups, followed by '-diol'
• Classes of alcohols


  • Primary
  • Secondary
  • Tertiary
• Primary alcohol


  Only 1 carbon directly bonded to the hydroxyl carbon
• Secondary alcohol


  Two carbons directly bonded to the hydroxyl carbon
• Tertiary alcohol


  Three carbons directly bonded to the hydroxyl carbon
• Alcohols are able to form hydrogen bonds between their functional groups
• Alcohols have higher boiling points than expected due to strong intermolecular forces
• Alcohols are very water soluble as they can form hydrogen bonds with water

  
• Length of carbon chain in alcohols

  The longer the chain, the less soluble the alcohol is
• Complete combustion of alcohols

  Produces carbon dioxide and water
• Incomplete combustion of alcohols

  Produces carbon, carbon monoxide and water
• Potassium or sodium dichromate are commonly used as oxidising agents for alcohols
• For alcohol oxidation reactions, heat and acidified conditions are required</b>

  
• Oxidation of primary alcohols

  Produces an aldehyde (with CHO group) and water

  
• Oxidation of aldehydes


  Further oxidation produces a carboxylic acid

  
• Oxidation of secondary alcohols

  Produces a ketone and water
• Tertiary alcohols cannot be oxidised in normal laboratory conditions
• Reflux setup for alcohol oxidation

  Round-bottomed flask with acidified oxidising agent, connected to a vertical condenser

  
• The condenser prevents volatile aldehydes from escaping, allowing further oxidation to carboxylic acid

  
• Distillation setup for alcohol oxidation

  Round-bottomed flask with reactants, connected to a horizontal condenser with a receiving flask

  
• Distillation stops the aldehyde from further oxidation
• Reflux is preferred as it ensures all reactant is converted to product
• Reflux of primary alcohols requires 2 moles of oxidising agent, distillation requires 1
• Dehydration of alcohols


  Reaction with concentrated phosphoric acid to produce an alkene and water
• The water is formed from the alcohol functional group and adjacent hydrogen
• Dehydration is an elimination reaction as a smaller molecule (water) is eliminated
• When an alkene is produced, E/Z isomerism should be checked