I know that $\ce{SeO2}$ readily affects the allylic position. The reaction mechanism of this reaction goes like this:

Seleniumdioxide oxidation
(Source: Wikipedia; License: Public Domain)

But, in my book, there's another reaction given as an exception:

formation of alpha-diketone

Here, an $\alpha$-diketone is formed.

Why and how is this alternative product formed? What is the mechanism for this product?

  • $\begingroup$ $\ce{\alpha}$-diketones are often formed when $\ce{SeO2}$ reacts with alkynes that don't have any hydrogens on the carbons adjacent to the acetylenic carbons. Are you sure your book showed an alkene? $\endgroup$
    – ron
    Commented Nov 1, 2015 at 23:32
  • $\begingroup$ Yes, for sure, I have checked it again and its an alkene not alkyne. I know that alkyne reaction but this is not that. $\endgroup$
    – shaistha
    Commented Nov 2, 2015 at 8:23
  • $\begingroup$ I found formation of an $\alpha$-diketone from a ketone, but not from an alkene. $\endgroup$
    – TAR86
    Commented Mar 13, 2019 at 5:54


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