Oh, if you think nitrogen triiodide is volatile stuff, check out the substances being synthesised in the Klapötke Lab. These people are bolting together chains of nitrogen atoms, in the hope of alighting upon explosives that don't produce corrosive or toxic by-products. One of the substances they produced was so unstable, it blew up
whilst they were trying to obtain an infra-red spectrum from less than a milligram of it. Just one milligram destroyed a Raman spectrometer. One of the papers published recently from the lab was entitled
The CN7- Anion. That's right, a carbon atom with
seven nitrogen atoms attached thereto in a chain. Not satisfied with manufacturing this anion, they then set about combining it with all sorts of cations to see if this would stabilise the anion. The sodium salt is reputedly no more hazardous than sodium azide, but the lead salt is the stuff that flying glass shards and shrapnel - in quantity - are made of. It's a basic rule of thumb that large cations with lots of electron shells, in combination with unstable anions, are hideously explosive. Big, fluffy cations like lead and mercury lend themselves admirably to the production of bangy substances (see, for example, mercury fulminate, whose name alone tells you what it's like). When you combine these with wacky chains of nitrogen atoms, you have a recipe for some very big and loud bangs indeed.
It's even worse if your nitrogen complexes contain at least one nitrogen atom that is forced to maintain a formal positive charge. Nitrogen atoms don't like this one bit, so nitrogen complexes with such atoms in them have a desire to fall apart at the drop of a hat. Klapötke's laboratory is cooking up quite a few of these at the moment, so if you have academic access to JACS, you can have lots of fun finding out how the Klapötke Lab is finding new ways of propelling its lab apparatus out of the window.
One discovery that contained a few surprises, centres upon something rejoicing in the wonderful name of heaxnitrohexaazoisowurzitane. Isowurzitane is a sort of cage complex of carbon and nitrogen atoms, which itself is, shall we say,
interesting to handle. Then, for good measure, the chemists bolted a whopping
six azo groups onto it, which is enough to make many more reasonable chemists reach for their running shoes. Not satisfied with that, they then bolted
six nitro groups onto it (nitro groups, NO
2, are always good for loud bangs, e.g., TNT). The mere mention of the words "hexanitro" alone makes many sane people want to be a
long way away from the test tube fast. To the surprise of the chemists who cooked this up, the molecule is surprisingly resistant to shock, vibration, etc., to an extent that would not be suspected from its molecular structure, which suggests that there's some interesting bond interactions going on in this molecule. However, when you detonate it, it packs one hell of a punch.
The point to remember here, is that nitrogen atoms have a longing to become stable N
2 molecules. Because these molecules contain a triple bond, once they're formed, they're resolutely stable. It takes a hell of a lot of energy to break them apart (e.g., Haber process for ammonia manufacture, the basis of the world's fertiliser industry). Trouble is, weird complexes of nitrogen atoms want to convert themselves to N
2 with a
lot of passion, so to speak, and from the standpoint of thermodynamics, this is
not a gentle slope. Those nitrogen chain complexes have
huge amounts of bond energy just itching to wind up as heat, and they have a habit of going all the way to N
2 without any gentle steps to less energetic intermediates. To say that the decomposition of these weird chains is a violently exothermic process, is like saying the Pope is a Catholic. When all that fizzing bond energy is dumped into a small region of space during the decomposition, the result is lots and lots of extremely hot nitrogen gas, which has a habit of expanding
very quickly indeed. Some of these molecules can produce expanding shock waves whose speed goes beyond the supersonic, and enters the fast
hypersonic realm. When your shock front is travelling at something like Mach 5, you know you're dealing with something special.
The aim of people such as the bods at the Klapötke Lab, is to find a chain of nitrogen atoms (or, in some of their more exotic experiments, a ring system!) that remains stable until you set it off. Stable enough, that is, to withstand the sort of handling they'll receive on a battlefield, packed into shells, being dropped by untrained or partly trained soldiers, fired out of guns, etc., only detonating when the fuse says "party time, boys!" They haven't hit found this particular pyrotechnic and chemical holy grail yet, but they're giving it their all looking for it. You can find out more about their activities
here. Enjoy the twee manner in which they describe their experimental explosives as "energetic materials". You know they're dealing in seriously bangy stuff, when the chemicals in question have names involving multiple invocations of phrases such as "aminotetrazole", "nitrotetrazolate", etc. One of their compounds, guanidinium azotetrazolate, has the alarming formula C
4H
12N
16 ... yes, there's
sixteen nitrogen atoms in that one, all waiting to strut their thermodynamic stuff and send shrapnel heading your way at several times the speed of sound. That's before we start talking about octanitrocubane (yes,
eight nitro groups bolted to a cubane cage ...).
