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Things I Won't Work With

Things I Won’t Work With: Chlorine Azide

Well, it’s been a bit too serious around here this week. So I thought today I’d step back to a period when men were men and chlorine azide was a reactive, toxic, and unstable compound that was only good for finding out what sort of explosion it would set off next. What’s that? You say that that’s still about all it’s good for? Staying power, that’s what I call it. If you work with the halogen azides, you work with things whose essential character time does not alter.
“Until they blow up”, you say. Ah, but that is their essential character. It’s the things around them that alter. Make sure you don’t put anything next to them that you’re not comfortable seeing altered – you know, all sudden-like.
A reader forwarded this 1943 JACS article, the first comprehensive study of chlorine azide, and it’s a joy to read. Part of the fun is, of course, watching these folks set off the fireworks. (The challenge with a substance like chlorine azide is finding something that it won’t react with violently):

Owing to the extreme instablity of the compound accurate determinations of the bioing and melting points have not been made as yet. Numerous explosions, often without assignable cause, have occurred during the experiments. . .”

Another thing I always enjoy in these papers is the list of recommended protective gear. No leather suits this time and (interestingly) no earplugs. Nope, it’s straight to the Iron Man look. These azidonauts endorse:

“. . .masks and breast-plates of sheet iron worn by observers during times of danger. Each mask is provided with a rectangular pane (7 x 3 inches) of shatter-proof glass. Although scores of violent detonations have occurred, with resultant demolition of much apparatus, no personal injury has been suffered.”

That last part is sort of a “no graduate students were maimed during the course of this research” statement, which really is good to know. But another nice thing about this paper is the way some parts of it are written, in a style which was a bit formal and archaic even for 1943. A sample:

“If small pieces of yellow phosphorus be added, with stirring, to a solution of chlorine azide in carbon tetrachloride at 0C, the solution gradually becomes turbid, and a succession of slight explosions takes place beneath the liquid. If stirring be omitted until the maximum turbidity is attained, the slightest agitation results in a detonation that demolishes the apparatus. . .”

Do not be omitting the stirring, then. I have to say, not being used to this sort of chemistry, that if I saw these events going on in my fume hood that a series of slight explosions might well take place beneath my iron breastplate. What else doth chlorine azide detonate with? Well, in case you had any doubt, the gaseous reagent “reacts violently” with sodium metal. They had four explosions at -78C, while the fifth run (persistence!) yielded a mixture of sodium chloride and sodium azide. (Actually, the other runs probably yielded that, too, albeit as a fine haze). I really have to salute the dedication involved in finding that out, though – after two or three violent explosions, you or I might be tempted to just say that we couldn’t determine the products of the reaction. But they were made of sterner stuff back in 1943.
The date does make me wonder if there was war research money involved; I wouldn’t be surprised. But chlorine azide has not been weaponized, nor will it be. It remains, with its chemical relatives, off in a part of chemical science that’s safe from human exploitation. It’s a spacious game preserve, that territory, and over the gate is the ornate motto Noli me tangere. Take heed.

61 comments on “Things I Won’t Work With: Chlorine Azide”

  1. Hap says:

    It is nice to have articles where the destruction is both fun to watch (from far enough away) and limited to one’s hood, basement, or specially designed room with blowout walls.

  2. Anonymous says:

    We’ve said it before, Derek… Put all this in a book!
    (You might want to correct the second sentence.)

  3. anchor says:

    Indeed a very interesting paper. The authors also laments about the fact that they could not determine its melting point (after freezing the same to -100 C), owing to several explosions along the way! These reagents in a formal sense still have a value in organic chemistry. For e.g. one can add to the double bond chloro/bromo azide, involving either NCS/NBS in the presence of sodium azide.

  4. I miss the 40s
    How doth the little azide
    Detonate his volatile tail,
    And pour the fires of the Nile
    On every weighing scale.
    How vigorously he seems to stretch and bend,
    How neatly spreads his triples,
    And welcomes naive chemists in
    With a succession of slightly explosive ripples

  5. Derek Lowe says:

    Anon – fixed the sentence, thanks.
    And Wavefunction, how doth the little crocodile, indeed!

  6. TwoYaks says:

    I second the echo for a book. You must have 10% of a 200 pager already written. Throw in some pictures of blown up stuff, and you could bump that to 15%. I’d definitely buy a copy. I love these posts.

  7. Anonymous says:

    I love their archaic language. It gives a distinct “here there be dragons” flavor to their research. It makes a nice warning to those who would pierce the veil of halogen azide chemistry to pay attention (and maybe consider leaving it un-pierced).
    You could totally make a book out of theses. Expand the selections a bit, add some chemical structures and reactions (including hilarious ones where the intermediates are all angry question marks and the product is a destroyed fume hood).

  8. Anonymous says:

    If the following link be followed, a biography of the article’s prinicpal author be obtained:

  9. Anonymous says:

    Did anyone notice the footnote in the paper? “This article is based upon parts of the thesis presented to the Faculty of the Graduate School of Cornel1 University by Joe
    Frierson in partial fulfillment of the requirements for the degee of
    Doctor of Philosophy.” I wonder if that “partial fulfillment” part means he decided it was time to cut his losses and get out while he still had fingers.

  10. Zach says:

    The “partial fulfillment” bit is standard — look at any dissertation’s signature page. While the dissertation is the primary requirement, it is by no means the only one.

  11. partial agonist says:

    I remember some med chem papers in that era where they describe the effects of what they made: “slight euphoria, a little diarreah…”

  12. myma says:

    Re (9) Very funny. Cornell theses all say that. The other partials are the course work, the oral exams, the pound of flesh, …
    In the physics/chemistry library, there is a room with all the bound theses, so one could find Dr Frierson’s and see what other fun things he did.
    This blog entry reminds me of the safety video I had to watch back in the day on effectiveness of safety glasses. It consisted of a test dummy with various kinds of eye and face protecting gear being shot at with paint balls.

  13. HK says:

    Yay, levity!

  14. Tim McDaniel says:

    The “archaic language” is merely the subjunctive mood. It’s mostly gone out of style, but there are still uses, as in “If we were [not was] to add chlorine trifluoride, the reaction would be more exothermic” or “It was required that we go [not went] to the back of the line” or “I ask that he be [not is] shown mercy”.

  15. Anonymous says:

    #14 Tim McDaniel:
    You could be right, or maybe Frierson was a “Lord of the Rings” fan.
    Oops, never mind. Tolkien hadn’t written it yet. Maybe he was a Monty Python fan…

  16. pete says:

    ..however, despite yer best intentions, Derek, we still seem to be on the subject of risky business. *BANG*

  17. I plugged my ears just reading the compound name.
    Book, Derek. I’ll buy it.

  18. milkshake says:

    Here is another candidate for things I would never work with – volatile organoarsine compounds – atrociously smelly, poisonous, irritant and pyrophoric.
    “During his study of cacodyl cyanide, Me2AsCN, prepared by reaction of “cacodyl oxide” with a concentrated aqueous solution of mercuric cyanide, an explosion cost Bunsen the partial sight of his
    right eye and, as Roscoe reports, “Bunsen was almost fatally poisoned, lying for days between life and death.” Bunsen recovered and completed his study.
    After distillation of the “cacodyl oxide”/Hg(CN)2 reaction mixture, the cacodyl cyanide formed beautiful, prismatic crystals underneath the water layer. These were quite volatile (mp 32.5 °C).
    They were dried by pressing them between sheets of
    blotting paper. Bunsen notes that it is absolutely
    necessary to carry out this operation in the open air while breathing through a long glass tube that extends to fresh air far beyond the volatile crystals.
    Bunsen reports that the vapor from 1 grain (0.0648 g) of cacodyl cyanide in a room produces sudden numbness of the hands and feet, and dizziness and insensibility to the point of unconsciousness. The tongue becomes covered with a black coating. These effects, however, are only temporary, with no lasting problems. (Bunsen lived to the ripe old age of 88.)”

  19. Sanjay Batra says:

    We could work with it and publish the paper
    2010-Eur. J. Org. Chem.-4705-4712
    So we need some compliments for accomplishing that. Not too difficult if generated in situ but yes temperature should not exceed 10 oC

  20. milkshake says:

    there is also a procedure for making 1,2 diamines from olefins that uses NaN3 (2 equivs) and I2, it proceeds by displacement of the iodine in the iodoazid intermediate (which is probably formed by IN3 addition). These bisazido compounds are very touch so one would make them in diluted acetonitrile and reduce them in situ.

  21. gippgig says:

    I wonder if anyone has ever tried to make chlorine triazide…

  22. Jose says:

    Weekly research meeting with “Brownie” –
    “So, how many sets of apparatus have you blown up this week?”
    “Excellent! Were they pulverized or just shattered?”
    “Fully pulverized, sir.”
    “Excellent progress! Wait for even more turbidity then…”

  23. processchemist says:

    Halas, once upon a time I was quite familiar with low MW trialkyl phosphines, in a lab where spring was announced by a flame when you were disconnecting the recovery flask of the distillation of triethyl or trimethyl phosphine. An environment where men were men and some of them were dangerous idiots happy to make arsine by reduction af arsenic trioxide…

  24. metaphysician says:

    Who was it, many posts ago, who noted that the plurality of your articles were on either halogens or azides? 😉
    So, as a non-chemist, I’m going to make a wild guess: Fluorine Azide is actually safer and more stable than Chlorine Azide. The F bonds tighter, making explosions less likely.

  25. Paul says:

    Waiting for a post on francium chemistry.

  26. Rick says:

    To Paul, 25: Francium would be exciting to work with if you could get your hands on enough of it (the current record is 10,000 atoms in one place at one time) and do the chemistry fast enough (it’s half-life is 20 minutes, decaying to radium). No wonder it’s been said that “Francium is so fragile, it’s basically useless.” (Sam Kean in “The Disappearing Spoon”)

  27. Joe Loughry says:

    Write that book! “Things I Won’t Work With:”
    I’ll buy it.

  28. Chris Buckey says:

    Add me in as another definite buyer should a “Things I Won’t Work With” book ever be published.

  29. Bored says:

    Explosions and science go hand-in-hand. It is why I got interested in science in the first place.
    In 1971 in 11th-grade chemistry, on the first day of class our teacher Mr. Tidwell walked casually into the room sipping coffee. He walked over to the demonstration table, and picked something up from underneath it with tongs and dropped it into the sink. About 5 seconds later there was a loud bang, which blew water up to the ceiling tiles and all over the chalkboard. After the screaming and laughter ended, he said, “Be careful in here.”
    I said to myself, “This is the best class I’ve ever taken.”

  30. sigma147 says:

    The scariest bit is the fact that there are basement chemists out there trying to make this stuff:
    Take it away, Darwin awards!

  31. Euro2cent says:

    > Book, Derek
    Sudden flashback to my misspent youth, when a certain “Bo Derek” took a sizeable proportion of printed photos in magazines …

  32. username says:

    that’s some mighty impressive grammar indeed. nobody bothers with “if it *were*” these days, let alone “*be* they”

  33. Anonymous says:

    Things i won’t work with: a certain chem manager at Roche who was recently jettisoned in the reorg. Smirky, biased, self absorbed, highly opinionated, severe favoritism, weak accomplishments. How could someone last so long on so little??????

  34. Anonymous BMS Researcher says:

    As Zach said, that “partial fulfillment” stuff is standard boilerplate on every thesis at most institutions. A grad student in my department even sent out invitations to the party celebrating her defense with the title “A Party Thrown In Partial Fulfillment…”
    A Google search on
    thesis submitted in partial fulfillment of the requirements for
    got more than 800 thousand hits.

  35. Jose says:

    OT, but highly ah, *interesting*-
    In silico tox “clearly predicted general toxicity risks (class III), and genotoxic alerts (polycyclic aromatic hydrocarbons, halogenated benzene and H-acceptor-path3-H-acceptor)”
    Slaps forehead….

  36. D says:

    Sigma147: Because a person working on mg scale is such a danger *eyeroll*
    Derek…I work with stuff like this kinda regularly. If you are interested in writing a book and want a co-author with first-hand experience ..let me know here (the email addy I post with is fake)
    I will tell you to watch Inorganic Chemistry’s ASAPS in the upcoming month…a new compound you will enjoy will be there…

  37. DCRogers says:

    #34: re: “thesis submitted in partial fulfillment of the requirements for” gets 800,000 hits.
    Just had to try the obvious next experiment — “thesis submitted in full fulfillment of the requirements for” gets only 52…

  38. Cymantrene says:

    I have found this quote in a Gaussian output:
    A.J.MERER AND R.S.MULLIKEN, CHEM.REV. 69, 645 (1969)

  39. Norepi says:

    @ #24: I can’t tell if you’re being facetious or not. I’m willing to bet that fluorine azide is even worse. The reactivity of the halogens gets attenuated a bit down the column.
    I’m giving my students a problem with iodine azide this week, and I’m just waiting for someone to ask what azides are and if halogen azides are for real.

  40. Bored says:

    If you type in “making chlorine azide” right now on Google, 4 of the top 5 hits are to this blog. The 3rd is to the link mentioned by #30 sigma 147.

  41. Ron says:

    #39: The citation is incorrect – the page number should be 639-656, but the quote itself is on page 645. I’d take a pressurized oxygen/ethylene mixture any day over chlorine azide, though.

  42. D says:

    39: But in covalent compounds F is usually more stable. ie NF3 is more stable than any of the other nitrogen trihalides.

  43. Hap says:

    If you follow the first link in the article, Dr. Lowe already posted on this. Based on the description, FN3 is significantly worse than chlorine azide. In addition, getting to it is much worse (HN3? F2? No, no, no $&%^ing way.)
    I’m guessing FN3 isn’t very covalent, but probably polar with +F-N3- – as you go down the halogen column of the Periodic Table, the halogens are less electronegative and more capable of stabilizing a positive charge, and vice versa, so F desperately does not want a (+) charge and is really unhappy when it has to have one.

  44. Norepi says:

    @ 43 – my sentiments exactly. Not really covalent, and gets the all around 10/10 on the nasty-o-meter.

  45. Hap says:

    Milkshake (#18) – That reference (Organometallics, 20(2001), pp. 1488-1498) is a potential “Things I won’t work with” article right there. The description of Me2AsAsMe2 is pretty good:

    it is a clear colorless liquid, heavier than and not miscible with water. Its odor is extremely repulsive, reminiscent of the odor of arsine. Even small amounts are extremely lachrymatory and cause an almost unendurable, long-lasting irritation of the nasal mucous membranes. Exposure to the vapors for a longer time causes nausea and oppression of the chest. The liquid causes violent itching when in contact with the skin. Its taste(!) is similar to its odor and it is very toxic.

    Seyferth also notes that Me2AsCl has a much worse (how?) odor than Me2AsAsMe2 and much worse physiological effects. Wow.

  46. JR says:

    No. Not only am I *NOT* a chem major, (organic or otherwise), had I tried to be one, I would, in all probability, have left this plane of worldly existence long ago. . . .
    Despite all of this, I regularly return to this blog to discover what new ways of absolutely destroying thousands of dollars of equipment he has come up with THIS TIME.
    These articles are hysterically funny, along with containing pointed advice for the would-be chemist. Where I teaching the subject, these articles would be required reading – there are too many things that can go “bump in the night” for no apparent reason; one does not have to add carelessness or stupidity to the mix.
    If that book ever gets written, I will buy several. Like “Ignition!”, it would be destined to become a classic!
    (Hint! Hint!)

  47. O'Brien says:

    It seems halogen azides are alive and well in the literature. This is quite a convenient procedure if you have the right kit in the lab:

  48. Hap says:

    #36: You mean this? (via this post at C+E News’s blog)
    One of the most sensitive compounds that Klapotke’s worked with? Yep, that sounds like a “Thing I Won’t Work With”.

  49. Richard Gadsden says:

    Rumour has it that someone is working on HeBeO.
    Yep, they finally got a something reactive enough to stick to helium. Are they mad?

  50. Richard Gadsden says:

    Rumour has it that someone is working on HeBeO.
    Yep, they finally got a something reactive enough to stick to helium. Are they mad?

  51. Ken says:

    Every time I read one of these, I kick myself harder for not sticking it out in chemical engineering. “Take off and nuke the site from orbit” is for mere tyros; this is the real stuff. 🙂

  52. Andrew Cummins says:

    Write the book!
    I came across the blog by accident – the “Thing I Won’t work with:” columns are priceless,
    — Andrew

  53. Andrew Cummins says:

    Write the book!
    I came across the blog by accident – the “Thing I Won’t work with:” columns are priceless,
    — Andrew

  54. cacogen says:

    Pardon my ignorance, I’m not a chemist. Why are halogen azides so dangerous? Why be there dragons in the land of azide chemistry?

  55. cacogen says:

    Pardon my ignorance, I’m not a chemist. Why are halogen azides so dangerous? Why be there dragons in the land of azide chemistry?

  56. Lurker says:

    @36: Yikes!!!!! One look at the structure in that link made my blood curdle. TEN nitrogens in a chain with only two carbons?! Whoa!!! No wonder the background picture has shattered pieces of equipment… I’m surprised the fragments aren’t smaller!

  57. Wotsallthisthen says:

    Very funny and interesting article. Who would ever expect a Chemist to be this funny? Well, maybe you all are and I just couldn’t stand the smell long enough to find out.

  58. Anonymous says:

    @29 – Yeah, I remember my sophomore chemistry (getting it as a junior meant taking “physical science” first instead of skipping straight from Biology). My chemistry teacher walked into class on the first day, picked up a Gummi Bear, and dropped it into an angled test tube over a burner (which I now know was aqueous potassium chlorate); the resulting bright flame and jet-engine stream of hot gases out the other end got our attention pretty quickly.
    Another one that got me interested was in college, involving some interesting but overall rather tame reactions, called “Copper From Start to Finish”. You begin with an arbitrary workable amount of pure copper metal, and start by chucking it in nitric acid (in a fume hood) to produce the nitrate (and nitrous oxide), then adding sodium hydroxide solution to precipitate out copper hydroxide, which is washed, dried and then heated to convert it to copper oxide, before chucking it in sulfuric acid to produce the sulfate, and then finally some zinc is added in to produce zinc sulfate and precipitate out pure copper again. Filter, rinse, dry, weigh, and wonder in the law of conservation of mass. I think in our lab we skipped the nitric acid part (rather nasty stuff, that), and instead used hydrochloric to produce copper chloride and hydrogen gas (much more environmentally friendly though you’d still want it in the fume hood), before continuing with the lye solution.

  59. David Edwards says:

    Interestingly enough, Wikipedia’s brief entry on chlorine azide contains the following little snippet:
    “Regulatory information : Its shipment is strictly forbidden by the US Department of Transportation.”
    No kidding?
    I love the rather twee manner in which they introduce this compound with:
    “More so than other azides, chrlorine azide is highly explosive. In undiluted condition, it usually detonates violently whatever the temperature, without apparent provocation.”
    I suspect someone is already trying to devise a synthesis pathway not only for the triazide, but the heptazide as well (if it exists). If indeed it can be shown to exist, and to be amenable to synthesis, chlorine heptazide should be a real barrel of laughs. In much the same way that discovering that a W87 warhead you’re standing next to is not only live, but is about to detonate in the next 30 seconds …

  60. David Edwards says:

    Meanwhile, for those who want to have fun with multiple azide groups, I give you: silicon tetrazide. Described on the Wikipedia page thus:
    “This high-energy compound combusts spontaneously and can only be studied in a solution.”

  61. David Edwards says:

    Meanwhile, noting the tangential diversion above on arsenic compounds, there’s one really evil one for interested parties to look up. It’s known as Lewisite, after the chemist who first prepared it. I’ll let those with journal access find out more about this, because the less said in public about how to make it, the better. Though the prep is so fraught with dangers, because of the nature of this end product (as if the reactants weren’t troublesome enough), that it won’t be featuring in any idiot’s basement chemistry repertoire. Anyone trying the synthesis outside a government lab with negative pressure glove boxes and remote manipulators, will kill themselves doing this, and the ensuing death will be a hideous one – so hideous that if there is a Hell, it will be regarded as blessed relief from the tortures this substance inflicts upon those exposed to it.

    This interesting compound was manufactured as a chemical weapon in World War I. I happen to have the joy of living in the town whose chemical works were approached by the then War Ministry here in the UK, and offered lots of money to make this substance in quantity to drop on German trenches, before it was banned under the Geneva Convention. Knowing what I do about this compound, the thought of a World War I era chemical plant making this right next door to residential areas, should elicit pants-filling terror in everyone reading this. A better candidate for Derek’s TIWWW series will be hard to find.

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