Propan-1-ol Oxidation (Edexcel International AS Chemistry): Revision Note

Core Practical 7: Oxidation of Propan-1-ol

Oxidation of propan-1-ol

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

  • When propan-1-ol is oxidised, propanal is produced and when oxidised further propanoic acid will be formed

Synthesis and purification of propanal and propanoic acid 

• Carefully add 20 cm³ of acidified potassium dichromate(VI) solution, K₂Cr₂O₇ (aq), to a 50 cm³ pear-shaped flask and cool the flask in an iced water bath

• Set up the reflux apparatus keeping pear shaped flask cool

• Place anti-bumping granules into the pear shaped flask 

• Measure out 1 cm³ of propan-1-ol 

• Using a pipette, slowly add the propan-1-ol drop wise into the reflux condenser

• When the propan-1-ol has been added remove the ice bath and allow to warm up to room temperature 

• Position the flask over an electric heater or in a water bath and heat for 20 minutes 

  • Propan-1-ol is flammable, therefore naked flames should not be used when heating which is why the use of an electric heater or water bath is an important safety precaution 

• Purify the product using distillation apparatus 

Reflux apparatus for the oxidation of propan-1-ol to propanoic acid

Distillation apparatus for the oxidation of a primary alcohol to an aldehyde by acidified K₂Cr₂O₇ (the equation in the diagram shows ethanol forming ethanal; propan-1-ol forms propanal in the same way)

Hazards, risks and precautions

• The alcohols used are flammable, e.g. propan‐1‐ol, butan‐1‐ol, pentan‐1‐ol, and their vapour can irritate the eyes and airways

• The alcohols should be kept away from naked flames, e.g. a Bunsen burner

• Avoid contact with the skin and breathing in the vapour

• A fume cupboard can be used to avoid breathing the vapour

• Use small amounts of each chemical to reduce the risk

• Potassium dichromate(VI) is a strong oxidising agent, so keep it away from flammable substances and anything that burns easily, and avoid skin contact with the solid

• Spillages should be mopped up right away with plenty of water