Oxidation of secondary alcohols to ketones
When a secondary alcohol is oxidised, it is converted to a ketone. The hydrogen from the hydroxyl group is lost along with the hydrogen bonded to the second carbon. The remaining oxygen then double bonds with the carbon. This leaves a ketone, as R1-CO-R2. Ketones cannot normally be oxidised any further because this would involve breaking a C-C bond, which requires too much energy.
The reaction can occur using a variety of oxidants.
The orange-red dichromate ion, Cr2O72-, is reduced to the green Cr3+ ion. This reaction was once used in an alcohol breath test.
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The reaction is performed under standard conditions, at room temperature, with either dichloromethane or trichloromethane. The reaction takes between half an hour and two hours to complete. The products are then separated from the byproduct, an iodide compound.
The by-products are dimethyl sulfide (Me2S), carbon monoxide (CO), carbon dioxide (CO2) and - when triethylamine is used as base — triethylammonium chloride (C6H15NHCl). Dimethyl sulfide and carbon monoxide are very toxic and volatile compounds, so the reaction and the work-up needs to be performed in a fume cupboard.
Oppenauer oxidation↑Jump back a section
- Burton, George et al. (2000). Salters Advanced Chemistry: Chemical Ideas (2nd ed.). Heinemann. ISBN 0-435-63120-9
- Dess, D. B.; Martin, J. C. J. Am. Chem. Soc. 1991, 113, 7277-7287.
- J. S. Yadav, et al. "Recyclable 2nd generation ionic liquids as green solvents for the oxidation of alcohols with hypervalent iodine reagents", Tetrahedron, 2004, 60, 2131-2135
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