AQA A Level Chemistry

Revision Notes

4.2.3 Distillation of a Product from a Reaction

Distillation of an Organic Product

REQUIRED PRACTICAL 5

Distillation of an organic product:

  • Distillation is a common practical completed in organic chemistry
  • For this course, the most common practical in which you will come across distillation and reflux apparatus is the oxidation of primary and secondary alcohol
  • This required practical gives you the opportunity to show that:
    • You can use an electric heating mantle rather than a Bunsen burner for heating
    • Use laboratory apparatus for a variety of experimental techniques and can set up glassware successfully
    • Safely and carefully handle different liquids, including those which are corrosive, irritant, flammable and toxic

The Distillation Process:

  • To  produce an aldehyde from a primary alcohol the reaction mixture must be heated
  • The aldehyde product has a lower boiling point than the alcohol ( since it has lost the H-bonding) so it can be distilled off as soon as it forms

Carbonyl Compounds Synthesis of Aldehydes, downloadable AS & A Level Chemistry revision notes

Heating under Distillation Apparatus

  • The reaction mixture needs to be heated until it boils using a heating mantle
    • Electric heating mantles are used for this because the temperature can be controlled, and because you are using chemicals which are flammable
  • Quickfit apparatus is then set up, including a pear shaped flask, a still head and a condenser
  • A Quickfit thermometer can be used, with the thermometer bulb sitting exactly where the vapours will pass into the condenser
  • A steady and constant stream of water passes through the condenser in a ‘water jacket’ – it enters at the bottom of the condenser and the drainage pipe removes the water from the top of the condenser
  • The distillate which forms in the condenser drips directly into a receiving vessel
    • The distillate which should be collected, is that which is given off at +/- 2 oC of the boiling point of the desired product
    • Some distillate may be given off below this temperature – this needs to be discarded and a clean vessel used to collect the desired product
    • Stop collecting the distillate if the temperature rises above +/- 2oC of the boiling point of the desired product
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