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DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

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March 18, 2009

Things I Won't Work With: Chalcogen Polyazides

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Posted by Derek

The Klapötke group at Munich are some of the masters of alarming chemical structures, and they basically seem to own the field of chalcogen azides. Perhaps the competition for this class of compounds is not as intense as it might be - the other labs doing this sort of thing are collaborations between USC and various military research wings. But they're still interesting beasts.

A few years ago, both groups reported the synthesis of tellurium azides, with the Munich group sending in their paper a few days before the USC/Air Force team sent in theirs. The parent tetra-azide was explosive, to be sure, but could be kept at room temperature without necessarily blowing up. Klapötke's group and the USC group (led by Karl Christe) then teamed up to tackle the corresponding selenium analogs, which were reported in 2007.

And they're a livelier bunch. The selenium tetra-azide is another yellow solid, like the tellurium compound, but it's rather harder to keep it down on the farm. Taking some selenium tetrafluoride (see below) and condensing it with trimethylsilyl azide at -196 °C did the trick. After warming things up (you'll note the relative use of that term "warming"), they saw that:

"Within minutes, the mixture turned yellow, the color intensified, and a lemon-yellow solid precipitated while the reaction proceeded. Keeping the reaction mixture for about 15 min at -64 °C resulted in a violent explosion that destroyed the sample container and the surrounding stainless-steel Dewar flask."

Did I mention that this prep was performed on less than one millimole? Spirited stuff, that tetra-azide. The experimental section of the paper enjoins the reader to wear a face shield, leather suit, and ear plugs, to work behind all sorts of blast shields, and to use Teflon and stainless steel apparatus so as to minimize shrapnel. Hmm. Ranking my equipment in terms of its shrapneliferousness is not something that's ever occurred to me, I have to say. It's safe to assume that any procedure which involves considering which parts of the apparatus I'd prefer to have flying past me will not get much business in my lab, no matter how dashing I might look in a leather suit.

That procedure deserves a closer look, though. You can't just crack open a can of selenium tetrafluoride whenever you feel the urge, you know. That stuff has to be made fresh, as far as I can see, and the way these hearty sons of toil make it is by reacting selenium dioxide with chlorine trifluoride. Yep, that stuff, the delightful compound that sets sand on fire and eats through asbestos firebrick.

So if you're going to make selenium polyazides, your day starts with chlorine trifluoride and I'm sure that it just rolls along from there. Before you know it, you've gone from viciously reactive halogens, paused to prepare some disgusting selenium fluorides, made some violently unstable azides that explode if you stick your tongue out at them and hey, it's dinnertime already. . .

Comments (25) + TrackBacks (0) | Category: Things I Won't Work With


1. Fred on March 18, 2009 9:58 AM writes...


I am used to having your essays me to a dictionary quite often. This time I'm not even going to try.

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2. Hap on March 18, 2009 10:26 AM writes...

and, hey, it's dinnertime already...

Only if you survive.

Christe and Klapotke are on the "read for entertainment, but don't try this at home (or anywhere else)" list.

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3. John on March 18, 2009 11:20 AM writes...

I wonder how he recruits graduate students ?

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4. SRC on March 18, 2009 11:32 AM writes...

Evel Knievel meets chemistry.

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5. Jose on March 18, 2009 11:36 AM writes...

This really makes me wonder how much fascinating chemistry is hiding out there in the dark, just waiting for someone who isn't afraid of things like ClF3 to go and discover it.

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6. Industry guy on March 18, 2009 11:47 AM writes...

shrapneliferousness....classic Derek....classic

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7. milkshake on March 18, 2009 11:58 AM writes...

problem with developing chemistry based on nasty reagents is that you then have to convince the fellow chemists the result is worth the hassle/hazzard.

I have seen an article manuscript with some medchem interest (that my boss got to review) about a cyclization that involved cyanogen azide. They were making N3CN in solution from BrCN and used it as such so there seemed to be no terrible danger - just the nuisance of working with BrCN - but I was wondering how many medicinal chemists would eagerly start on series of compounds with expectation that they will have to cook up a fresh cyanogen azide every time...

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8. CMC Guy on March 18, 2009 2:04 PM writes...

I maintain that majority of chemists have pyromaniac tendencies so recruitment of grad students probably not difficult. I also assume such labs have appropriately high level precautions so are probably safer there than most undergrad chem labs (although guess the real fun stuff is no longer practiced). Working in a plant (in most parts of the world at least) surrounded by drums and even tanker cars has greater potential but much less probability for a fire/explosion than an R&D lab.

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9. Hap on March 18, 2009 3:59 PM writes...

I think chemists like fires well enough - it's the setting themselves on fire (or the shattering their body into lots of pieces/requiring facial reconstruction and/or plastic surgery/requiring a shoebox funeral) parts of Klapotke's work that might make it hard to recruit grad students and postdocs. You have to ask yourself at some point if your lab skills are good enough, with the knowledge that if they aren't very bad things are more likely than usual to happen.

His group safety training is supposed to be good, though, and perhaps if one is interested enough, youth and perceived indestructibility win out over fear.

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10. SR on March 18, 2009 7:25 PM writes...

Actually if it was a toss up between being in Klapotke's lab working with highly dangerous reagents, but with the proper equipment and with some other group that works with explosive reagents on the side but with minimal protection.... well time to suit myself up in leather and get rolling.

Meaning, I can see how somebody who is interested in a career working with explosives will find his group an attractive option.

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11. Rhodium on March 18, 2009 8:28 PM writes...

First, I wonder how the auditors at USC respond to purchase orders for leather suits.
Second, I have not laughed so long and hard since reading Mark Twain's take on James Fenimore Cooper. Classic!

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12. doctorpat on March 18, 2009 10:24 PM writes...

I wonder why the USAF is interested in the horrible stuff.

Either they are hoping to stumble on something useful like an "island of stability" to refer to an old nuclear theory... or they really want to be able to generate extremely high temperatures and pressures if you know what I mean.

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13. You're Pfizered on March 19, 2009 8:27 AM writes...

Great stuff.

Famous last words of an explosives chemist:

"Hey, look! There's a solid precipitating out!"

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14. Chemjobber on March 19, 2009 10:27 AM writes...

doctorpat: I think it's the island of stability, rather than explosives. That particular branch of AFRL is the "Space and Missile Propulsion Division" -- they're interested in things that can make rockets and satellites go.

Note to all new grads or underemployed folks: if you're willing to take the risk and/or look at changing concentrations, you might consider propellant/explosives research. The government seems to be hiring, as their workforce retires. Granted, a lot of all this funding seems to be Air Force-directed, which seems to be getting the short end of the funding stick these days.

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15. You're Pfizered on March 19, 2009 11:09 AM writes...

We are all looking for the Island of Stability. Isn't that where Superman lives?

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16. Hasufin on March 19, 2009 12:25 PM writes...

You know, I have to wonder about the sanity of anyone who would think "Hey, let's combine two of the nastiest, most dangerous compounds we can find and see if they synthesize anything interesting!"

Now, given the properties of chlorine trifluoride, I'm pretty confident it can yield some truly remarkable results... but I'm still dubious than any sane person would want to work with it.

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17. Rhenium on March 19, 2009 2:10 PM writes...

Two observations on the Klapotke paper,

1) The paper starts with "In memory of..." not exactly an auspicious way to begin the paper.

2) More credit must go the crystallographer who was willing to stick a slab of said material into his goniometer.

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18. Sili on March 19, 2009 2:46 PM writes...

no matter how dashing I might look in a leather suit.
I'm tempted to do a LOL-chemist: "Camp. Ur doin it rong"

As a onetime chrystallographer in training I'd love to try that sorta thing out.

Of course no sensible chemist would let me near explosives. I had terrible labskills.

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19. Bored on March 19, 2009 8:30 PM writes...

That is what made me want to become a scientist... the possibility that a miscalculation could result in angering some chemical bonds. It must be like the primeval desire to kill the mastodon before he stomps us.

It would be easier to kill a deer, but the mastodon is just so much more fun!

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20. Jonadab the Unsightly One on March 23, 2009 8:41 AM writes...

How do you recruit grad students for a group like this? Easy. First, you tell them how many times your group has been published in the last four years, and then you tell them that you are doing cutting-edge research in propellants and explosives. At least 5% of them will immediately think, "Cool!", and you've got them sold.

The brain may then go through the motions of finding out more information in order to make an informed decision, but in practice the decision is already made, emotionally, and the brain just has to catch up. So when you tell them you're working with ClF3, their brain may object (Cl and F together? That sounds more or less completely unsafe), but they'll be looking for ways to talk themselves out of the objection, which you can supply by telling them you take precautions, blast shields and so forth. Since they WANT to talk themselves out of the objection, this will be enough for many of them. I mean, think of the ego boost, being able to go to parties and tell people, "I work with rocket propellants and high explosives. It's pretty exciting. Yesterday we synthesized a chemical that blew the sample container halfway across the room." You'll always have an audience for that kind of tale!

With that said, you wouldn't get *me* in the same building with that kind of research.

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21. kbiel on April 22, 2009 1:40 PM writes...

So, now we know what Happy Fun Ball™ is made of.

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22. Ramu on March 24, 2010 10:01 AM writes...

Hi, what about the explosive nature of polymeric polyazides such as a poly(azido ethylene)?

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23. Gridlock on November 14, 2011 6:31 AM writes...

Garibaldi: No boom?
Sinclair: No boom.
Ivanova: No boom today. Boom tomorrow. There's always a boom tomorrow.
[Sinclair and Garibaldi exchange an exasperated look and wander off.]
Ivanova: What?! Look, somebody's got to have some damn perspective around here. Boom. Sooner or later. BOOM!


Susan Ivanova: Ambassador, do you really want to know what's going on down there right now?
Londo Mollari: Yes, absolutely.
Ivanova: Boom. Boom, boom, boom. Boom, boom. BOOM! Have a nice day.
[She walks away with a smile, leaving Londo to stew.]
Londo: Faugh! You can never get a straight answer from anyone around here!


Grandly entertaining, well for those folks still alive.

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24. Kenny Strawn on December 29, 2013 10:53 PM writes...

I wonder if anyone has ever made a tetraazide of sulfur yet...

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25. David Edwards on February 27, 2015 11:02 PM writes...

@Kenny Strawn: Why stop at the tetrazide? With sulphur, it's possible, in theory at least, to make a hexazide. Now whilst Derek is probably reaching for the heart medication at the mere mention of the word 'hexazide', there's something else to consider here, namely that a sulphur atom is somewhat more compact than, say, a selenium atom. To use Derek's terminology, making azides from big, fluffy cations is a sure fire way of discovering new and interesting ways of making your lab apparatus travel at several miles per second across the lab. This is why, for example, mercury azides are strictly for the deranged. Though in the case of sulphur, the nice, compact atom would be offset by the fact that, in theory at least, you could bolt six azide groups onto it, resulting in a compound that would almost certainly qualify for another of Derek's adjectives - "hopping". :)

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