Oxidation of secondary alcohols to ketones using PCC
Description: Treatment of secondary alcohols with pyridinium chlorochromate (PCC) leads to ketones.
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Real-World Examples
Org. Synth. 1929, 9, 52
DOI Link:
10.15227/orgsyn.009.0052
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Org. Synth. 1937, 17, 43
DOI Link: 10.15227/orgsyn.017.0043
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Org. Synth. 1941, 21, 18
DOI Link: 10.15227/orgsyn.021.0018
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Org. Synth. 1955, 35, 39
DOI Link: 10.15227/orgsyn.035.0039
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Org. Synth. 1965, 45, 28
DOI Link: 10.15227/orgsyn.045.0028
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Org. Synth. 1962, 42, 36
DOI Link: 10.15227/orgsyn.042.0036
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Hi, is there disadvantages/advantages to using the different reagents (PCC/H2CrO4/Swern Oxidation/KMnO4)?
“On paper” they all carry out equivalent transformations.
In practice…. well, H2CrO4 has toxic chromium (VI) so we try to avoid it, plus it’s strongly acidic which can affect acid-sensitive groups on the molecule. PCC is milder from an acidity standpoint but will tend to form gums/tars at the bottom of your flask, plus it has the toxic chromium issue. The Swern is a nice oxidation to use, especially on large scale, but it does have the disadvantage that you have to run it at -78°C and you generate a lot of foul-smelling dimethyl sulfide (DMS). [a related but well-performing oxidation is done with SO3-pyridine complex, the Parikh-Doering oxidation]. KMnO4 is a wild beast that will also oxidize alkenes, so avoid if at all possible. Dess-Martin periodinane is popular because it’s a weighable white solid that does the job simply and effectively (although it does have a high molecular weight and is probably not best for large-scale applications).
Generally speaking the Parikh-Doering and Dess-Martin Periodinane won’t get you into many problems.
I hope this answers your question! James
How about the selective oxidation of benzylic alcohol via MnO2 ? We use that in class in synthesis problems.
Good suggestion!
If the byproducts are H2CrO3 and pyridinium chloride then bond G should never be formed and the bond J should be a bond formed with O-H
i was convinced with the mechanism of oxidation with chromic acid.. but, i wondered how does pcc work as a selective reagent here?!! now i understand how it does…
Glad you found it helpful Payel.