what happens when acetone is oxidised by selenium oxide?
It depends on how much SeO2 you have inside there. anything stopping the other methyl group from being oxidized as well. For the SeO2 oxidation of alkenes, both the initial allylic alcohol product as well as the final (doubly oxidized) a b-unsaturated ketone can be formed depending on the conditions. the reaction stops after single oxidation.
So, the final product we get is 3 C with two ketone group attached at 2 C atoms.