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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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January 7, 2009

Things I Won't Work With: Azidotetrazolate Salts

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Posted by Derek

An early favorite has appeared in my “most alarming chemical papers” file for this year. Thomas Klapoetke and Joerg Stierstorfer from Munich have published one with a simple title that might not sound unusual to people outside the field, but has made every chemist I’ve shown it to point like a bird dog: “The CN7 Anion”. The reason that one gets our attention is that compounds with lots of nitrogens in them – more specifically, compounds with a high percentage of nitrogen by weight – are a spirited bunch. They hear the distant call of the wild, and they know that with just one leap of the fence they can fly free as molecules of nitrogen gas. And that’s never an orderly process. If my presumably distant cousin Nick Lowe does indeed love the sound of breaking glass, then these are his kinds of compounds. A more accurate song title for these latest creations would be “I Love the Sound Of Shrapnel Bouncing Off My Welder’s Mask”, but that sort of breaks up the rhythm.

These Bavarian rowdies have prepared a series of salts of the unnerving azidotetrazolate anion. As they point out, the anion was described back in 1939 (in what I hope was a coincidental association with the outbreak of the Second World War), but its salts are “rarely described in the literature”. Yes indeed! People rarely spray hungry mountain lions with Worcestershire sauce, either, come to think of it.

After reading this paper, I’m considering taking my chances with the mountain lions. The authors report a whole series of salts, X-ray structures and all, which range from the “relatively stable” lithium and sodium derivatives all the way to things that couldn’t even be isolated. In the latter category is the rubidium salt, which they tried to prepare several times. In every case, the solution detonated spontaneously on standing. And by “spontaneously”, they mean “while standing undisturbed in the dark”, so there’s really just no way to deal with this stuff. It’s probably a good thing they didn’t get crystals, because someone would have tried to isolate the hideous things. The cesium salt actually did give a few crystals, which they managed to pluck from the top of the solution and get X-ray data on. A few hours later the remaining batch suddenly exploded, though, which certainly must have been food for thought.

The authors went on to investigate the thermal behavior of these wonderful compounds, another risky move. As it turns out, they have calorimetry data on only five of the salts, because when they got to the sodium derivative, “a violent explosion destroyed the setup”. They also did sensitivity tests, using a standard drophammer rig from the Bundesanstalt fuer Materialforschung, evocatively abbreviated as BAM. These, along with the friction and spark tests, put these compounds well into the “primary explosive” category. Well, the ones that they could get data on, that is: the potassium and cesium compounds blew up as they tried to get them into the testing apparatus. So it’s safe to assume that they’re a bit touchy, too.

One of my favorite parts of the paper is the mention (found in much of the recent high-energy materials literature) that high-nitrogen compounds are worth investigated as “green” explosives, which makes me think that the whole environmental-rationale business must be reaching its end points. The notion of a more environmentally friendly way to blow things up aside, I have to salute the paper’s authors. They’ve made compounds that no one will have to make again, and survived the experience. Read the paper and be glad that this wasn’t your PhD project. . .

Comments (43) + TrackBacks (0) | Category: Things I Won't Work With


1. emjeff on January 7, 2009 1:33 PM writes...

you chemists are a fun bunch...

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2. Great Molecular Crapshoot on January 7, 2009 1:40 PM writes...

I remember one of the lecturers from my undergrad days talking about silver ketenides. Apparently they were a little on the sensitive side (I won't follow up your Nick Lowe breaking glass comment with a cheap, gratuitous jibe at rabid feminists)and it was thought that they could be used as fly-killers. This was because a fly landing on a surface treated with a silver ketenide would be sufficient to cause detonation. Probably urban myth but the imagery is irresistable.

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3. Sili on January 7, 2009 3:22 PM writes...

It's interesting, actually. We'll always have to blow stuff up, but how big is the impact of the explosive relative to all the dust and rubble from the building that comes down?

I guess it could make sense to use for rocks and stumps.

“a violent explosion destroyed the setup”

I love it! As a failed crystallographer I'd be torn between going "oooooh. Awesome!" and being worried about my much to expensive toy.

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4. Maks on January 7, 2009 4:30 PM writes...

Klapoetke and his group were always on top of the annual security lecture. I remember one accident where the PhD student had multiple fracture in his hand when he tried to recrystallize a few mg of the compound. I might be exciting to wear a leather coat, blast shield and special gloves while working behind bulletproof glass.....

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5. Indy on January 7, 2009 4:45 PM writes...

Did they report if the compounds tasted salty, bitter, sweet, etc.?

Oh, Cmon! Don't tell me they didn't try that!


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6. psi*psi on January 7, 2009 6:24 PM writes...

Klapoetke and his students must be absolutely insane. I'm not in their field, and never will be (since I do enjoy the use of both my hands...), but I still read every paper that comes out of the group. Pure entertainment!

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7. DTL on January 7, 2009 6:25 PM writes...

Heh, heh. I love these posts on wacky (and highly nitrogenous) compounds. There's a recent book on these (Organic Chemistry of Explosives) with a lot of stuff that's almost as bad. (I think I'm the only one to have taken it out at my library ever.)

Tetraazidomethane always gets me. Twelve nitrogens to one carbon.

Hey, green explosives aren't too bad of an idea. Mainly, finding more environmentally friendly ways to make more stable and easier to use compounds. For example, dinitrogen pentoxide is a "green" nitrating agent; it already contains the nitronium ion!

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8. Zemyla on January 7, 2009 7:07 PM writes...

Four of the compounds you've reviewed are fluorides, and four are azides. Most notably, one is both.

I may not be a chemist, but I'm starting to think those functional groups may be dangerous!

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9. Chemjobber on January 7, 2009 10:36 PM writes...

I was actually contacted about a postdoc with their American counterparts, seeking to transfer some of this work. I (and my fingers) are pleased to have been able to turn them down.

It's actually worth noting that one of the few niche areas that are really hurting for warm bodies are explosives research. I could be wrong, but my reading seemed to indicate that this was something that the US gov't was seeking to rectify.

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10. Bored on January 7, 2009 10:45 PM writes...

I agree with Derek on the environmental-rationale business reaching its end point. Remember, there was a time in geologic history when oxygen was a deadly poison, as environmentally un-friendly as it gets.

I wonder if the Los Alamos physicists are working on environmentally friendly nuclear weapons?

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11. daen on January 7, 2009 11:38 PM writes...

Apropos azide chemistry, TotallySynthetic blogged Hayashi's 3-pot synthesis of Tamiflu recently, one of who's steps is an acid chloride displacement by azide ... details here -->

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12. Morten G on January 8, 2009 5:06 AM writes...

@3. Sili

It's not like macro crystallographers don't try to get messy. RIP is basically collecting your data, then pounding your crystal with tons of radiation, and then collecting data again from the sorry remains of your crystal. With micro focus beams you can actually cut tiny holes directly through your 100K crystals. This is fun but does kinda prevent you from collecting anymore on that particular crystal.

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13. Indy on January 8, 2009 9:58 AM writes...

I guess this is the only research group in the world when the grad students need to call the bomb squad to open their hoods!

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14. milkshake on January 8, 2009 10:35 AM writes...

I think their (quasi)rationale is that some tetrazoles are pretty stable and could be advantageous as gun propellants because the produced gases will are less corrosive. In terms of performance, I think tetrazoles will never measure up to nitramines.

Also there are several known high-performance insensitive explosives that are routinely disposed off by incineration in a furnace.

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15. Anonymous on January 8, 2009 10:56 AM writes...

"I wonder if the Los Alamos physicists are working on environmentally friendly nuclear weapons?"

Remember the neutron bomb, which supposedly killed people but spared property?

We're now working on the neutrino bomb, which spares *both* people and property.


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16. Hap on January 8, 2009 1:09 PM writes...

When you see Klapotke or Christe's names on a paper you know that 1) you're probably pretty glad that someone else and not you is working on that topic and 2) you hope that whatever they're making won't be dropped on you or used to fire missiles at you at some point.

Considering the issues that states have with DOD over perchlorate contamination from propellants, less persistent or toxic propellants and explosives might not be such a bad idea. Considering their friction and shock sensitivities, though, these aren't it - it's nice to be able to load the compounds into a device, and better if the grunt assigned to move the device about can't take the facility out if he drops it.

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17. Sigivald on January 8, 2009 1:20 PM writes...

Bored: Project Plowshare, part 2?

I remember when I was in freshman Chemistry (which is as far as I got), back when carbon only got to have four things directly attached to it.

None of this fancy "seven" or "twelve" stuff!

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18. Anonymous BMS Researcher on January 9, 2009 7:58 AM writes...

I don't work on ebola virus either!

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19. Paddywhacker on January 10, 2009 11:56 PM writes...

Imagine the problems determining an LD50 for these compounds, especially if it was in the order of grams per kg.

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20. metaphysician on January 12, 2009 12:14 PM writes...

It could be worse, there's trying to figure the LD50 of ClF3. . .

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21. Hap on January 12, 2009 12:53 PM writes...

Why bother? I don't know if OSHA/EPA will accept "toxic effects are trivial at all known dosages compared to the thermal/chemical/explosive effects at those dosages", but that would be my story.

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22. Bill on January 12, 2009 7:12 PM writes...

In Grad school, we had a Frenchman downstairs doing work on the echem of highly nitrogenous polyaromatic rings. Starting from one nitro group and proceeding upwards until it was no longer stable to work with. His nickname: Fearless Francois

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23. Bored on January 13, 2009 10:14 PM writes...

I've thought of the ultimate "environmentally friendly" nuclear weapon. Remember episode 23 of the original "Star Trek" series called "A Taste of Armageddon?" A nuclear war was being waged between two planets in a virtual way, then the actual casualties were sent to disintigration chambers. Lots of dead people resulted, but hey, the environment was saved.
We are headed there, you know.

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24. Disgusted on January 15, 2009 12:17 AM writes...

I am actually very sad to see that not one of you so-called scientists have ascended beyond the trivial desire to pour righteous scorn on the work of a few people who are actually willing to take risks in order to learn something new and maybe make this world slightly safer for the rest of us. One of you actually had the balls to jibe that he (or she?) 'does not work on ebola virus either'. Guess what Dr. Safety - *someone* has to work with Ebola virus. It's not optional. Risk-taking by the few ensures the safety of the many. That's the whole point of this sort of stuff. Next thing you will be gleefully pointing fingers at soldiers, firefighters, emergency medical personnel, mine rescue workers, etc. etc. doing dangerous things in the line of duty.

Yes, working with scary chemicals is not safe. Please tell me - how is making milligram quantities of experimental explosives under carefully controlled conditions less safe than working in an L4 biohazard environment, handling vanishingly small quantities of stuff that not only might kill the experimenter, but - if let lose - can kill hundreds of other people?

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25. Paul on January 24, 2009 1:33 AM writes...

You know us chemists. If something goes boom we have to see if we can make it.

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26. Myself on February 11, 2009 4:23 PM writes...

All I can think when reading this stuff is "We're gonna need another Timmy!"

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27. Matthew Goldfinch on January 8, 2010 4:02 PM writes...

A) ""[E]nvironmentally friendly" nuclear weapons" would no doubt mean ones with negligible radioactive fallout, for eample the Proton-Boron Process except more amenable to chaining (p + B-11 -> 3 He-4).
B) I (an undergrad) have nothing against working on the Ebola virus, I just feel uncomfortable even thinking about people working on it except by telepresence with some sort of napalm or ClF3 decontamination sprinklers or something in case something goes badly wrong.

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28. Matthew Goldfinch on January 8, 2010 5:23 PM writes...

A) ""[E]nvironmentally friendly" nuclear weapons" would no doubt mean ones with negligible radioactive fallout, for eample the Proton-Boron Process except more amenable to chaining (p + B-11 -> 3 He-4).
B) I (an undergrad) have nothing against working on the Ebola virus, I just feel uncomfortable even thinking about people working on it except by telepresence with some sort of napalm or ClF3 decontamination sprinklers or something in case something goes badly wrong.

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29. Mark on December 24, 2010 6:27 AM writes...

I quite like the idea of environmentally friendly explosives and nukes. Most firearms use lead-based primary explosive in their primers, which is a health hazard on indoor firing ranges since it's dispersed in an easily inhalable fine powder. The few existing non-toxic primers don't have the same shelf life.

Nukes without fallout would enable project Orion to actually be seriously re-considered, as well as allowing nukes to be used as mining explosives, seismic surveying, and ground shattering for geothermal plants, let alone the obvious appeal of clean nuclear power.

Just because you want to blow something up doesn't mean you don't care if the area is poisoned at the same time.

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30. Gerald Smith on June 9, 2011 5:18 AM writes...

Here's a fun azido compound for the suicidal to make a name for themselves isolating and characterizing for the first (and probably last) time: Azidopicrin! N9,NO2C. Just reflux some gentle friendly chloropicrin in acetonitrile with sodium azide. Anybody wanna bet that it is a transparent oily liquid that explodes if you just look at it mean? Surely there must be some German chemists out there.....

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31. Write A Book on March 8, 2012 9:47 PM writes...

Unless youre a master you will not be able to effectively do that.

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32. Anonymous on September 28, 2012 6:45 PM writes...

azido say what?

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33. Anonymous on September 28, 2012 6:45 PM writes...

azido say what?

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34. johnBoy on September 28, 2012 6:46 PM writes...

azido say what?

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35. Yikes on December 29, 2012 8:53 PM writes...

Somehow I can just see Herr Professor Kloepotke and his studenten donning their pickelhaube amd lederhosen before tackling a new synthesis...

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36. John on February 28, 2013 6:58 PM writes...


I think this is your funniest column yet, although that's like ranking your chosen subject molecules as "the most explosive yet," there being no real way to ascertain that short of counting the number of times a given lab has had its windows replaced. As an A+ student in organic, I thought MY prof was funny, with his off-color jokes, like "Now men, be sure your tube doesn't overflow like a hot ROOT (beer). (NOT appreciated by the women). But you, my friend, are in a class by yourself. Keep up the good work--but always behind your welder's mask. We can't afford to lose you -- the planet needs all the humor it can get.

Fort Collins, CO

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37. John on March 3, 2013 3:23 PM writes...


Reading about the azidotetrazolate salts-cum-gases once again, I couldn't help but HOWL (again) at your remark about spraying hungry mountain lions with Worcestershire sauce. Having seen their handiwork on deer carcasses in the mountains, I came to the conclusion that the only thing I'd ever spray them with was capsicum oil (fortunately, I never had to). Still live,thanks to never messing with the felines OR the CN7 anion,I am yours truly,


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38. David Edwards on September 9, 2013 8:45 PM writes...

Apparently Klapötke et al have unleashed a paper describing an azotetrazole with ten nitrogen atoms chained together. The paper is this one:

I love the masterful understatement in the abstract:

"The title compound possesses both
exceedingly high explosive performance and sensitivity."

As if one would expect anything else from a Klapötke lab product ...

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39. David Edwards on September 22, 2013 4:01 AM writes...

I've been giving some thought to these polynitro compounds, and I doodled something on my pad that I think even Klapötke might think twice about synthesising. (Or, worryingly, might regard as a whole new "exciting" field).

Sadly I can't embed images in this post, but the doodle consisted of the following steps:

[1] Draw two 6-membered rings, composed entirely of nitrogen atoms, with single bonds throughout;

[2] Connect the two rings together with single bonds between two pairs of nitrogen atoms;

[3] Attach nitro groups to all remaining nitrogen atoms with unattached bonds. (8 in all).

Not sure what the IUPAC name for this beast would be (other than the -octanitro part, a designation that itself should cause chemists outside Klapötke's lab to undergo prolapse), but I suspect if ever it was made, it would not only constitute a pretty stunning achievement, but would be seriously energetic.

Now if only I can find a way of making this doodle appear in a post ...

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40. David Edwards on September 22, 2013 4:04 AM writes...

Oh, by the way, if you hit "preview" and your post contains characters outside the 7-bit ASCII set, such as vowels with accents, the post is mangled. Might want to do some bug checking on the software because of this. Pity my correct spelling of Klapötke went AWOL just because I hit "preview" then corrected some other typing errors.

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41. David Edwards on June 24, 2014 6:30 PM writes...

Derek, it appears that Klapötke and his team are not the only ones dealing in substances that wwell and truly fall into the heading of "Things I Won't Work With". I just found this paper:

The title alone will probably make you want to head for a concrete bunker, viz:

Two High Nitrogen Content Energetic Compounds: 3,6-Diguanidino-1,2,4,5-Tetrazine and Its Diperchlorate

So, the authors of this paper have not only made a high-energy nitrogen-rich molecule, but(and I'm hilariously imagining your heading for the foetal position when you read this!), they made a diperchlorate of the molecule in question, as if someone had dared the authors to come up with the most viciously explosive compound they could dream up in their most twisted nightmares.

Having seen what a comparatively benign perchlorate (I'm aware of how 'benign' is very definitely a relative term with perchlorates) could do at PepCon (though admittedly, they did have 4,000 tons of the stuff stored there), I'm having lots of fun imagining what just one gram of this latest molecule might be capable of. To use one of your choice aphorisms, this is a hopping compound indeed. :)

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42. Anonymous on June 24, 2014 6:41 PM writes...

Oh, for those who want to see this paper, and see for themselves the fun world of nitrogen-rich diperchlorates, here's a link:

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43. Getheren on July 14, 2015 11:29 PM writes...

7: That makes me wonder whether anyone has ever tried to synth up tetrapentazeniomethane. Assuming that's the proper systematic name for a carbon with four pentazenium groups hung off of it.

Or, as is more likely, barely attached to it and ready to fly off and be free the moment a stray photon comes by and gives a come-hither look.

If anyone's tried it, I'll bet Klapoetke has. And if he has, he's probably taken a stab at saturating just about everything conceivable with pentazenium groups. Octopentazeniumcubane, anyone? Hexapentazeniumhexanitroisowurtzitane? No, let's start small: tripentazeniumtoluene.

Why, yes, as a matter of fact I *do* have a sick mind. Thanks for noticing. :)

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