High-Nitrogen Anion Exceeds The Power Of RDX

In the quest for environmentally friendlier and more powerful explosives, researchers at Ludwig Maximilians University, in Munich, report the synthesis of a collection of azidotetrazolate (CN₇^–) salts that take a step toward both goals (J. Am. Chem. Soc., DOI: 10.1021/ja8077522). Thomas M. Klapötke and Jörg Stierstorfer synthesized the CN₇^– anion by deprotonating 5-azido-1H-tetrazole. The new salts have the highest nitrogen content reported for tetrazolate compounds. For example, the hydrazinium salt, N₂H₅CN₇, is 88.1% nitrogen by mass. These nitrogen-rich molecules are considered "greener" than traditional explosives because they generate fewer carbon-based by-products that can damage artillery gun barrels and the environment. The researchers' calculations indicate that N₂H₅CN₇ has the highest detonation pressure and velocity of the new compounds—values that exceed those of the powerful explosive RDX. Although hydrogen bonds help render N₂H₅CN₇ thermally stable at room temperature, the compound is still too sensitive to impact and friction for field use. Klapötke says adding a methyl group to the anion may reduce its sensitivity enough for it to be used safely.