How to oxidize secondary alcohols to ketones
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص544-545
2025-06-21
369
where you met the use of Cr(VI) in the form of CrO3. One common version of this reaction is the Jones oxidation, shown in the margin. The mechanism starts with the formation of HCrO4− ions, that is, Cr (VI), from dichromate ion in solution. In acid, these Cr (VI) species form chromate esters with alcohols. Chromate esters decompose by elimination of a Cr (IV) species, which subsequently reacts with Cr (VI) to yield 2 × Cr(V). These Cr(V) species can oxidize alcohols in the same way and are thereby reduced to Cr (III) (the final metal-containing by-product). Cr (VI) is orange and Cr (III) is green, so the progress of the reaction is easy to follow by colour change.
Chromic acid is best avoided if acid-sensitive alcohols are to be oxidized, and an alternative reagent for these is PCC (pyridinium chlorochromate), which can be used in dichloromethane.
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