Blogging a crystal structure a day in 2014


Contributed by

David Turner

A Nobel Explosive – Trinitroglycerin

After a bit of a break Dr Dave T. is back with an explosive post!

What does it look like?


What is it?

With the upcoming release of a new AC/DC album, I found myself raising a cacophony in the shower (note the deliberate avoidance of the word 'singing'). The lyrics "I'm TNT, I'm dynamite" got stuck in my head and made me realise that they're actually wrong (science fact not getting in the way of a good rock song). TNT (trinitrotoluene) is not dynamite, which is composite based on trinitroglycerin. The timing of this revelation is even more significant, as the Nobel Prizes have just been awarded and few people realise that Alfred Nobel, who bequeathed his estate to a trust to fund the prizes (including for peace) which bear his name, was the inventor of dynamite.

Nobel came from a family that was rooted in science and engineering, and Alfred's particular interest was in explosives, particularly nitroglycerin (1,2,3-trinitroxypropane). His research was in part aimed at making the compound more stable, particularly after an accident at his factory that killed 5 people including his younger brother. He invented dynamite, a composite of nitroglycerin with diatomaceous earth as an absorbent, which has increased stability and could therefore be handled in industrial uses (particularly mining). Military dynamite is not nitroglycerin-based.

The molecular structure of trinitrogylycerin is quite simple, being propane with three nitro groups (one at each carbon). The presence of nitro groups in small molecules is generally a theme of explosive compounds, and seeing too many in one molecule causes concern amongst synthetic chemists. The packing of the molecules in the crystal structure lacks any traditional 'strong' interactions such as hydrogen bonding. Instead the crystal structure is held together by van der Waals interactions and dipole-dipole interactions between the nitro groups.

Where did the structure come from?

The structure was determined and published in Acta Crystallographica C in 1984 by Espenbetov and co-workers (Acta Cryst. 1984, C40, 2096-2098). These are braver crystallographers than me, given that mishandling the material would lead to a bad case of, as Jazzy Jeff and the Fresh Prince said, 'Boom Shake the Room' (although I'm fairly certain the song is not about explosives).