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November 16, 2004
Things I Won't Work With: Ozonides
I've never done an ozone reaction myself. In fact, I haven't seen anyone else do an ozonolysis in years now, and I wonder if this reaction is passing into chemical history. These guys are hoping not.) Many chemistry departments have an electric gizmo to produce ozone in small quantities, and I get the impression that they're mostly gathering dust.
Ozone attacks a carbon-carbon double bond, initially making an ozonide, a hair-raising five-membered ring that has three oxygens in a row. That rearranges to a still-alarming one with two on one side, separated by carbons from the other. That falls apart on workup to two carbonyl compounds (or other things, depending on what you add to the reaction.) It's a very clean way to oxidize a double bond and make reactive handles out of its two ends.
But it tends to be something that's done on a small scale, because those ozonides are packed with energy and ready to hit the town. In general, we chemists shy away from compounds with lots of single bonds between the elements on the right-hand side of the periodic table. Those guys tend to have a lot of electron density on them, and bonding between them is a careful, arm's-length affair, sort of like porcupines mating. Two oxygens single-bonded make a peroxide, and those generally blow up. A small ring with more oxygens in it than carbons will almost invariably blow up if you try to concentrate it or handle it too briskly.
I'd do an ozonolysis if I needed to (although first I'd have to find our machine and see if it even works.) But you couldn't pay me to try to isolate the intermediate ozonides. But you can pay some people, like Prof. Pat Dussault, who was a post-doc down the hall from me when I was in graduate school. He's made a career out of oxygen-oxygen bonds, no small feat.
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