For conversion of primary alcohol to Aldehyde the selective
oxidizing agent is required which stops oxidation at Aldehyde stage
and do not proceed to carboxylic acid. The reagent useful for this
conversion is PCC and MnO2.
- PCC: Pyridinium chlorochromate. See structure in image file.
Preparation: Chromium (VI) oxide in HCl is added with pyridine and
extracted with dichloromethane. Selectivity is because the no free
chromate ion remains in solution due to complex formation.
- MnO2: Especially useful for Allylic and Benzylic
primary alcohol oxidation to Aldehyde. Work under mild and neutral
conditions.
- KMnO4 is strong oxidizing agent and gives carboxylic
acid as final product from primary alcohol. And
H2O2 hydrogen peroxide do not oxidize
alcohols.