• Aldehydes?and?ketones?are carbonyl compounds containing a C=O group
• They can be prepared from the oxidation of?primary?and?secondary?alcohols?respectively

Oxidising agents

• The oxidising agents used to prepare aldehydes and ketones from alcohols include?acidified potassium dichromate?(K2Cr2O7) and?acidified potassium manganate?(KMnO4)
• Acidified with dilute sulfuric acid,?potassium dichromate(VI), K2Cr2O7,?is an orange oxidising agent
  • When the alcohols are?oxidised?the orange dichromate ions (Cr2O72-) are reduced to green Cr3+?ions
• Acidified with dilute sulfuric acid,?potassium manganate(VII), KMnO4?is a purple oxidising agent
  • When the alcohols are?oxidised?the purple manganate ions (MnO4-) are reduced to colourless Mn2+?ions

The oxidising agents change colour when they oxidise an alcohol and get reduced themselves

Synthesis of aldehydes

• To make an aldehyde,?warm primary alcohol?is slowly added to the oxidising agent
• The formed aldehyde has a lower boiling point than the alcohol and can therefore be?distilled off?as soon as it forms
• The aldehyde is then condensed into a liquid and?collected

Aldehydes are formed from the oxidation of primary alcohols

Synthesis of ketones

• To make a ketone,?warm secondary alcohol?is slowly added to the oxidising agent
• Since the formed?ketone?cannot be further oxidised it does not need to be?distilled off straightaway?after it has been formed

Ketones are formed from the oxidation of secondary alcohols