Esters

• • Carboxylic acid + alcohol (+ strong acid catalyst- usually concentrated sulphuric acid ) —> ester + water
  • R1-COO-R2
  • R1 = acid
  • R2 = alcohol
  • condensation reaction - water is eliminated
  • reversible reaction
  • functional group of ester = -COO- (ester linkage)
  • Ester = alkyl carboxylate
  • alkyl from alcohol
  • carboxylate from carboxylic acids
  • methanol + propanoic acid —> methyl propanoate
• Uses of esters

  1. plasticisers - mixed into polymers to improve flexibility: PVC is rigid, used in drainpipes + window frames, when ester plasticiser is added it becomes cling film= more flexible
  2. solvents for organic compounds - volatile so easily separated from solute: ethyl ethanoate is cheap + low toxicity so is used in paints and nail varnish remover
  3. perfumes - esters have pleasant smells
  4. artificial food flavourings contain esters: ethyl methanoate = raspberry
• Hydrolysis

  • esters can undergo both acid and base hydrolysis

  1. acid hydrolysis: Ester + water —> carboxylic acid + alcohol (with sulfuric acid present) under reflux
  2. base hydrolysis: ester + OH- —> carboxylate ion + alcohol ( with sodium hydroxide) under reflux
• Fats + oils

  • glycerol + fatty acids —> fats / oils
  • glycerol = propane-1,2,3triol (alcohol)
  • fatty acid is a carboxylic acid
  • fats are saturated
  • oils are unsaturated
  • produced from condensation reaction of glycerol with three fatty acids

  
• Vegetable oils

  • unsaturated (mono / poly) - can also be found in nuts - known as essential fatty acids
  • cant pack closely together so weaker van der waals forces
  • lower melting point - liquids at room temperature
  • exhibits E-Z stereo isomerism
• Animal fats

  • saturated fatty acids - no double bonds so can pack tightly together
  • straight and uniform hydrocarbon chains
  • stronger van der waals forces
  • higher melting point - solids at room temperature
  • bad - can cause increase in bad cholesterol, stroke and heart conditions
  • Does not exhibit E-Z stereo isomerism
• Biodiesel 


  • Vegetable oil + 3 methanols —> glycerol + 3 methyl esters ( in the presence of potassium hydroxide catalyst)
  • biodiesel is a mixture of fatty acids made from methyl esters
  • Can be made from rapeseed oil

  
• Soap

  • Produced through hydrolysis of animal fats or vegetable oils
  • Heated with sodium hydroxide
  • e.g. Fats + 3 sodium hydroxide —> glycerol + soap ( in the form of sodium ionic salts)
  • need 3 sodium hydroxides as fats and oils have a glycerol with three fatty acids attached so each needs to be removed
  • ionic salt as COO- Na+
  • ionic so can dissolve in water ( property needed for it to be a salt as can be washed off)