Oxidation of Ethanol (OCR A Level Chemistry A): Revision Note

PAG 5.3: Oxidation of ethanol

• Primary alcohols can be oxidised to form aldehydes, which can undergo further oxidation to form carboxylic acids

• For example:

  • Oxidising ethanol produces ethanal

  • Ethanal can then be oxidised further to ethanoic acid

Synthesis and purification of ethanal and ethanoic acid 

1. Add 20 cm³ of acidified potassium dichromate(VI) solution (K₂Cr₂O₇) to a 50 cm³ pear-shaped flask

2. Cool the flask in an ice bath

3. Set up the reflux apparatus while keeping the flask cool

4. Add anti-bumping granules to the flask

5. Measure 1 cm³ of ethanol

6. Using a pipette, add the ethanol dropwise to the reflux condenser

7. Once all the ethanol has been added, remove the ice bath and allow the flask to warm to room temperature

8. Position the flask over an electric heater or in a water bath

9. Heat for 20 minutes

   • Ethanol is flammable - avoid naked flames

   • Use an electric heater or water bath for safety

10. Purify the product using distillation apparatus:

Practical skills reminder

• This practical demonstrates purification of a liquid product using:

  • Controlled reflux to ensure complete oxidation of the alcohol

  • Distillation to isolate and collect the target liquid (ethanal or ethanoic acid)

  • Appropriate safety measures for heating flammable reagents