Now this is a fine substance. Also known in the older literature as fluorine azide, you make it by combining two other things that have already made my “Things I Won’t Work With” list. Just allow fluorine (ay!) to react with neat hydrazoic acid (yikes), and behold!

Well, what you’re most likely to behold is a fuming crater, unless you’re quite careful indeed. Both of those starting materials deserve serious respect, since they’re able to remove you from this plane of existence with alacrity, and their reaction product is nothing to putz around with, either. The first person to prepare the compound (John F. Haller back in 1942) survived the experience, and made it (rightfully) the centerpiece of his PhD dissertation. But relatively few buckaroos had the fortitude to follow his trail over the years, and it’s not hard to understand why. Haller himself wrote on the subject in 1966 from an industrial position at Olin Mathieson, and got right to the point:

”(Fluorine azide) is described as a greenish-yellow gas at room temperature, liquefying at −82°C when diluted with nitrogen and freezing to a yellow solid at −143°C. Evaporation of this solid generally results in violent explosion.”

Yes, it does, and that does tend to slow down the march of science a bit. Not until 1987 was an improved procedure published, from Helge Willner and group in Hannover. (We’ll see him again – most of his publication list falls into the “Things I Won’t Work With” category, and I really have to salute the guy). Basically, it was the same reaction, but done slowly and Teutonically. You start off by making absolutely pure anhydrous hydrogen azide, which is a proposal that you don’t hear very often around the lab, and is the sort of thing that leads to thoughts of career changes. (Maybe I could go into the insurance business and sell policies to whoever took over the prep). The next step is introduction of the fluorine, and when elemental fluorine is the most easily handled reagent in your scheme, let me tell you, you’re in pretty deep. After the reaction, attention to painstaking fractional evaporation at very cold temperatures, in the best traditions of German experimental chemistry, is needed to clear out the reactants along with some silicon tetrafluoride, difluorodiazene, and other gorp. Willner’s group managed to make about 20 milligrams of the pure stuff, but strongly recommend that no one ever make more than that. As far as I can tell, no more than a few drops of the compound have ever existed at any one time. This is not really a loss:

”The synthesis of pure N3F by the method described above was repeated more than 30 times without explosion. But if N3F is cooled to -196 C or N3F is vaporized faster than described, very violent explosions may occur. One drop of N3F will pulverize any glass within a 5-cm distance.”

They managed to get pretty full spectroscopic data on the compound while they had it, which was good of them, and even explored its chemistry a bit. Life must have a peculiar vividness when your job is to come in and see if triazadienyl fluoride does anything when you expose it to fluorine monoxide. (Oddly, they report that that reaction is OK – go figure). Still, most of the literature on this compound remains computational, rather than experimental (other than Willner’s lab), and unless it turns out to be the secret to faster-than-light travel or something, that situation will continue to obtain. It’s already good for accelerating Pyrex fragments past the speed of sound, but there are easier ways.

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