Cubane

It’s interesting what you find when you’re looking for molecular structure files. I found this…

Now far be it from me to say anything about organic chemists having too much time and money, but you must admit that at first glance, research into ‘platonic hydrocarbons’ does seem a touch superfluous. Platonic hydrocarbons are so-called, because they’re molecules shaped like the platonic solids. Overwhelmingly unlikely to occur naturally, the three possible platonic hydrocarbons are tetrahedrane (C4H4), cubane (C8H8) and dodecahedrane (C20H20). It ought to be pretty obvious from the names which platonic solids they’re named after. Icosahedrons and octahedrons, incidentally, are simply not possilbe to make with carbon.

So cubane then. A chemical curiosity I stumbled upon while I was looking at hydrocarbons with 3D cage structures (like adamantane). Once upon a time, it was thought that carbon bond angles of 90° would be too strained to be stable. The normal bond angle for carbon is 109.5°, after all. As it happens, cubane is actually metastable once formed. It doesn’t decompose spontaneously, purely because there’s no readily accessible way for it to do so.

It turns out, cubane isn’t a waste of time and money at all! It’s quite an interesting little molecule. With the highest density of any hydrocarbon, it’s being investigated as a means of efficiently storing energy. Due to the strain on those bonds, it’s quite reactive too, in a similar way to acetylene (strained bonds store additional potential energy). As well as being investigated for use in medicine and nanotechnology, there’s a fair amount of potential for developing high energy density fuels from cubane.

One application being investigated is in explosives. Octanitrocubane is a high explosive, and a pretty impressive one too. High yield (estimated up to 25% higher than some military grade explosives), not detonated by shock, and breaking down into N2 and CO2 both starting chemical and decomposition products are essentially non-toxic. Only one problem — it’s so difficult to make that no one’s actually made enough to be tested as an explosive yet. Still, these things take time.

Personally, I have to wonder how well cubane would work as a form of rocket fuel…

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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