I have searched the whole internet but I could only see examples where the authors of the article took $\ce{R1}$ and $\ce{R2}$ as the alkyl groups around the carbon. This is regarding the oxidation of carbonyl compounds (I am specifically searching about ketones) using $\ce{SeO2}$. What I understood was $\ce{C=O}$ got introduced on the alpha-carbon and two hydrogens from that carbon were lost. Please tell me the product obtained on reacting pentan-2-one with $\ce{SeO2}$. Will the carbon having 3 alpha-hydrogens become $\ce{C=O}$ or will the other one having 2 alpha hydrogens become $\ce{C=O}$?


  1. Selenium dioxide oxidation of ketones and aldehydes. Evidence for the intermediacy of .beta.-ketoseleninic, K. Barry Sharpless and Kenneth M. Gordon Journal of the American Chemical Society, 1976, 98 (1), 300-301 DOI: 10.1021/ja00417a083
  2. https://www.adichemistry.com/organic/organicreagents/seo2/selenium-dioxide-seo2.html

The mechanism of Selenium Dioxide (Riley) oxidation proceeds via the enol tautomer of the ketone (see scheme - image from Wikipedia). If the ketone is assymetric and can enolise to either side then the reaction should give the two di-ketones in proportion to the amount of either enol formed though I cannot find any reference where this has been experimentally demonstrated. In the OP's case of 2-pentanone, a mixture of the two possible products will be formed.

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  • $\begingroup$ why would it not make a double bond as it does for 1,4 diketones? $\endgroup$ – user98209 Aug 27 at 14:34
  • $\begingroup$ @chemistry.stackexchange.com/questions/33034/…: It's depend on the several factors including structure of starting material, solvent, and pH. You can find an answer to your question here. $\endgroup$ – Mathew Mahindaratne Aug 27 at 16:40
  • $\begingroup$ you never answered the last part of my question ! the oxidation of 2 pentanone. the oxygen is introdeuced on the terminal carbon or on the 3rd carbon ? $\endgroup$ – raged ravager Aug 28 at 5:38
  • $\begingroup$ @ragedravager see the edit $\endgroup$ – Waylander Aug 28 at 7:45
  • $\begingroup$ thank you !!!!!!!!!!!!!!!!!!!!!!!!!! $\endgroup$ – raged ravager Aug 29 at 15:12

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