After nearly 20 years of effort, researchers have achieved the synthesis of octanitrocubane, a compound that could be one of the most powerful nonnuclear explosives known.
Philip E. Eaton and Mao-Xi Zhang of the University of Chicago and Richard Gilardi of the Naval Research Laboratory in Washington, D.C., report their feat in the Jan. 17 Angewandte Chemie International Edition.
Eaton synthesized the parent compound, cubane, in 1964. At the time, cubane had one of the highest densities of any known hydrocarbon—1.29 grams per cubic centimeter. Gasoline by comparison has a density of 0.8 g/cm3. “Gasoline floats on water,” he says. “Cubane sinks like a rock.”
In the early 1980s, Army researchers recognized that cubane derivatives, especially octanitrocubane, could pack an incredible punch. Since an explosion involves very fast combustion, high densities lead to big blasts, Eaton explains. “You go from a compact solid to a lot of gas and energy,” he says.
Octanitrocubane could be twice as powerful as trinitrotoluene (TNT), and “it’s thought to be 20 to 25 percent more effective than HMX [octogen], which is the state-of-the-art military explosive right now,” says Peter M. Gehring, a physicist at the National Institute of Standards and Technology in Gaithersburg, Md.
Adding the eight nitro groups to cubane proved to be a challenge. “The first four could be put on by manipulating functional groups”—that is, replacing components of an existing cubane compound, Eaton says. “The next four were much more painful. We had to develop new methodologies.”
Researchers haven’t yet made enough octanitrocubane to check its explosiveness, but tests on the small samples made by Eaton’s group show that the compound has a density close to 2 g/cm3.
Even though octanitrocubane may pack a powerful punch, it’s safe to handle. “The nice thing is that it’s shock insensitive, unlike TNT,” says Gehring. “You don’t blow your leg off carrying it around.”
What’s more, the compound fits another one of the military’s requirements for an explosive: Its byproducts won’t hurt the environment. Eaton notes, “It can kill you, but it can’t be toxic.”
Octanitrocubane should burn into carbon dioxide and nitrogen, he says.