Cube molecule is a real blast

It will knock spots off gelignite, blows holes in TNT and make Semtex look positively tame. Chemists have succeeded in synthesising a chemical they predict could be the most explosive substance yet short of a nuclear blast, writes Steve Farrar.

The creation of octanitrocubane, hailed as a significant step in chemistry in its own right, could lead to a whole new class of explosives. Philip Eaton and Mao-Xi Zhang, at the University of Chicago, in the United States, managed to make the substance for the first time after years of theoretical speculation, an achievement verified by Richard Gilardi of the Naval Research Laboratory in Washington DC. Calculations indicate it could be more powerful than the best non-

nuclear explosives.

The power of the cube-shaped molecule lies in the very reason why it has proved so elusive to the chemists - the high levels of energy stored in its bonds. The new chemical is based on cubane, whose molecular framework consists of eight carbon atoms held rigidly at the corners of a cube. This frame is under high strain as the carbon atoms are restrained at 90 degrees to each other while preferring to be separated by 109.5 degrees and can be easily burst, giving off energy.

The chemists had to attach a nitro group - which consists of a single nitrogen atom and two oxygens - to each of the corners of the cube to make the material. Nitro groups are fundamental to many modern explosives.

But tests have shown this first sample of octanitrocubane to be less dense than predicted, and hence a weaker explosive than it could be. In the electronic journal Angewandte Chemie International Edition, Dr Eaton said he was now looking for this denser form.