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I'm in an organic 1 class, and we learned about using periodic acid (HIO4) to cleave a glycol into two carbonyl groups, oxidizing the glycol. However, in the given reaction (see picture below), I'm skeptical that an oxidation as presented in our textbook (Organic Chemistry 6th Ed., Brown, Foote, Iverson, Anslyn) actually occurs. The mechanism presented in the textbook is analogous to the first step followed by the step labeled (A). This produces a ring with nine carbons and two carbonyl groups, which to me seems rather unlikely due to angle strain. The step labeled (B) seems like a more likely follow up to the first step, where a ring shift creates a spiro shaped bicyclopentane with a single carbonyl group.

Then again, with option (C), which ignores that first step, a Pinacol Rearrangement could occur, giving the same product as (B).

Which of these is most likely? I would think that B or C would be the mechanism since the final product seems much more stable. Normally we assume reactions are done in water unless told otherwise, so I don't see any reason why C couldn't also work. Reaction

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  • $\begingroup$ I wouldn't expect any significant angle strain in a 9-membered ring with 2 carbonyls. I see no reason why the reaction shouldn't proceed normally along path A. On page 3 of this link they note that the trans-1,2-diol with one more carbon atom than your molecule does not react with periodic acid - the implication being that the cis analogue does react. $\endgroup$ – ron Nov 30 '17 at 20:05

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