Applications and Occurrences of Heterocycles in Everyday Life 185In a chemical explosion, it is assumed that CHNO compounds are converted into carbon monoxide or dioxide (depend-
ing on the oxygen balance), water and nitrogen. The formation of these very stable molecules results in the release of a
considerable amount of energy and gas. It follows that many heterocycles, particularly high nitrogen compounds, are
highly energetic compounds, with the potential to be used as explosives.
Tetrazoles have the highest proportion of nitrogen and tetrazole itself is classifi ed as an explosive for transportation
purposes, although not used as such. Diazotetrazole (or the equivalent diazonium salt) has the requisite energy but is
exceptionally dangerous due to facile spontaneous detonation. 1,1-Azobistetrazole, which has a chain of ten nitrogen
atoms, is slightly more stable and can be isolated as a solid, but ‘attempts to manipulate the dry solid inevitably led to
extremely loud explosions and the destruction of labware’! However ‘Tetrazene’ is a safe commercial explosive, used
in detonators. 5-Aminotetrazole, which is not explosive in its own right, can release much energy (and large volumes
of gas) on decomposition as a component of mixtures, and is used in this way in vehicle air bag infl ators. Combining
the potential of a tetrazole with a suitable metal can produce a less polluting fi rework colorant, the example below
producing a red colour.
The saturated heterocycle RDX, a very widely used high explosive, is a component of Semtex and was used as a replace-
ment for TNT in the Second World War. The dangerously unstable acetone peroxide, which has been used by terrorists,
is ‘trimeric’ and contains a nine-membered ring, although dimers and tetramers can also be formed from acetone and
hydrogen peroxide. Acetone peroxides (and many other peroxides) are notorious amongst chemists as unwanted by-
products from hydrogen peroxide reactions, being extremely sensitive and prone to detonation.
3,5-Diamino-2,6-dinitropyridine N-oxide (DADNPO) has a high heat tolerance (up to 300 °C) and is therefore par-
ticularly suitable for use in oil wells. The related LLM-105, a pyrazine N-oxide, is a quite insensitive high explosive.
5-Nitro-1,2,4-triazol-3-one, which also has low sensitivity, has a wide range of explosive applications. Even a seemingly
innocuous compound such as 3,4-diaminofurazan (DAF; 3,4-diamino-1,2,5-oxadiazole) is under development.
A primary explosive is one that is used (in a small quantity) to initiate the detonation of the main (secondary)
explosive, which is usually diffi cult to detonate directly. The primary explosive is usually contained in a detonator or
ignition cap.