In CHE322 I often show the structure of TNT (trinitrotoluene) when discussing nomenclature of benzene compounds.  Organic compounds that are explosives frequently have one or more of the following features:

•Many nitrogen atoms (because the very stable gas N2 is formed during combustion)

•Oxygen (an internal source of oxygen to assist combustion)

•Highly strained bonds

For an example of the last feature, consider the molecule octanitrocubane.  That does not look like a happy molecule.

Octanitrocubane also demonstrates the first two features: a lot of explosives contain multiple nitro groups.

As an extreme example of the first point, this entry in the series of “Things I Won’t Work With” blog posts at Derek Lowe’s site is a fascinating read.  With a little chemical experience, the structure of such a nitrogen-rich, double-azide compound on a bottle label should make one want to run, quickly, away from it.