Everyone knows hydrogen peroxide, HOOH. And if you know it, you also know that it’s well-behaved in dilute solution, and progressively less so as it gets concentrated. The 30% solution will go to work immediately bleaching you out if you are so careless as to spill some on you, and the 70% solution, which I haven’t seen in years, provides an occasion to break out the chain-mail gloves.
Chemists who’ve been around that one know that I’m not using a figure of speech – the lab down the hall from me that used to use the stuff had a pair of spiffy woven-metal gloves for just that purpose. Part of the purpose, I believe, was to make you think very carefully about what you were doing as you put them on. Concentrated peroxide has a long history in rocketry, going back to the deeply alarming Me-163 fighter of World War II. (Being a test pilot for that must have taken some mighty nerves). Me, I have limits. I’ve used 30% peroxide many times, and would pick up a container of 70%, if I were properly garbed (think Tony Stark). But I’m not working with the higher grades under any circumstances whatsoever.
The reason for this trickiness is the weakness of the oxygen-oxygen bond. Oxygen already has a lot of electron density on it; it’s quite electronegative. So it would much rather be involved with something from the other end of the scale, or at least the middle, rather than make a single bond to another pile of electrons like itself. Even double-bonded oxygen, the form that we breath, is pretty reactive. And when those peroxides decompose, they turn into oxygen gas and fly off into entropic heaven, which is one of the same problems involved in having too many nitrogens in your molecule. There are a lot of things, unfortunately, that can lead to peroxide decomposition – all sorts of metal contaminants, light, spitting at them (most likely), and it doesn’t take much. There are apparently hobbyists, though, who have taken the most concentrated peroxide available to them and distilled it to higher strengths. Given the impurities that might be present, and the friskiness of the stuff even when it’s clean, this sounds like an extremely poor way to spend an afternoon, but there’s no stopping some folks.
Any peroxide (O-O) bond is suspect, if you know what’s good for you. Now, if it’s part of a much larger molecule, then it’s much less likely to go all ka-pow on you (thus the antimalarial drugs artemisinin) and arterolane, but honestly, I would still politely turn down an offer to bang on a bunch of pure artemisinin with a hammer. It just seems wrong.
But I have to admit, I’d never thought much about the next analog of hydrogen peroxide. Instead of having two oxygens in there, why not three: HOOOH? Indeed, why not? This is a general principle that can be extended to many other similar situations. Instead of being locked in a self-storage unit with two rabid wolverines, why not three? Instead of having two liters of pyridine poured down your trousers, why not three? And so on – it’s a liberating thought. It’s true that adding more oxygen-oxygen bonds to a compound will eventually liberate the tiles from your floor and your windows from their frames, but that comes with the territory.
These thoughts were prompted by a recent paper in JACS that describes a new route to “dihydrogen trioxide”, which I suppose is a more systematic name than “hydrogen perperoxide”, my own choice. Colloquially, I would imagine that the compound is known as “Oh, @#&!”, substituted with the most heartfelt word available when you realize that you’ve actually made the stuff. The current paper has a nice elimination route to it via a platinum complex, one that might be used to make a number of other unlikely molecules (if it can make HOOOH in 20% yield, it’ll make a lot of other things, too, you’d figure). It’s instantly recognizable in the NMR, with a chemical shift of 13.4 for those barely-attached-to-earth hydrogens.
But this route is actually pretty sane: it can be done on a small scale, in the cold, and the authors report no safety problems at all. And in general, most people working with these intermediates have been careful to keep things cold and dilute. Dihydrogen trioxide was first characterized in 1993 (rather late for such a simple molecule), but there had been some evidence for it in the 1960s (and it had been proposed in some reactions as far back as the 1880s). Here’s a recent review of work on it. Needless to say, no one has ever been so foolhardy as to try to purify it to any sort of high concentration. I’m not sure how you’d do that, but I’m very sure that it’s a bad, bad, idea. This stuff is going to be much jumpier than plain old hydrogen peroxide (that oxygen in the middle of the molecule probably doesn’t know what to do with itself), and I don’t know how far you could get before everything goes through the ceiling.
But there are wilder poly-peroxides out there. If you want to really oxidize the crap out of things with this compound, you will turn to the “peroxone process”. This is a combination of ozone and hydrogen peroxide, for those times when a single explosive oxidizing agent just won’t do. I’m already on record as not wanting to isolate any ozone products, so as you can imagine, I really don’t want to mess around with that and hydrogen peroxide at the same time. This brew generates substantial amounts of HOOOH, ozonide radicals, hydroxy radicals and all kinds of other hideous thingies, and the current thinking is that one of the intermediates is the HOOOOO- anion. Yep, five oxygens in a row – I did not type that with my elbows. You’ll want the peroxone process if you’re treated highly contaminated waste water or the like: here’s a look at using it for industrial remediation. One of the problems they had was that as they pumped ozone and peroxide into the contaminated site, the ozone kept seeping back up into the equipment trailer and setting off alarms as if the system were suddenly leaking, which must have been a lot of fun.
What I haven’t seen anyone try is using this brew in organic synthesis. It’s probably going to be a bit. . .uncontrolled, and lead to some peroxide products that will also have strong ideas of their own. But if you keep things dilute, you should be able to make it through. Anyone ever seen it used for a transformation?