[Inconspicuous]

Hey guys, I am writing a paper about investigating the structural features of explosives, and I looked at some compounds like TNT, RDX, Picric acid. I can tell straight away that the high enthalpy of combustion is due to the presence of nitrogen and oxygen, however, all these compounds have something like a cyclic carbon or nitrogen ring structure found within it, and I want to ask what is it about the presence of these rings that make them so desirable? aren’t delocalised rings supposed to decrease the enthalpy of combustion of the substances? I do not know much about these compounds, as it is my first time learning about explosives. TO reiterate, I am not planning on any synthesis whatsoever. I am simply investigating the features of the molecules which causes it to have a high enthalpy of combustion.

[rolnor]

I think octanitrocubane is the most powerfull explosive and this containes the very strained cubane-structure. So, its not optimal to have a aromatic ring as in TNT if you want a powerfull explosive but its cheap and stable.

https://en.m.wikipedia.org/wiki/Octanitrocubane

Edit: Its the fastest explosive, Iam not sure if its the most powerfull but very strong.

[Babcock_Hall]

Nitroglycerine does not have any rings.  Diacetone dioxide has a six-membered ring, but I am unaware of any strain.

[rolnor]

Its difficult to compare these, they are not stable as TNT or ONC. But I am not sure about the question anymore?

[Corribus]

Question is based on a false premise. For one, carbon rings are not a common feature of explosive compounds. The fact that rings appear in some of the well-known explosive compounds is completely coincidental, deriving from the fact that many of the early explosives were discovered unintentionally when chemists were just nitrating a lot of organic crap back in the 1800s. A lot of (but not all of) that crap had benzene rings because benzene rings are common in organic compounds. Six membered rings are quite stable and don't contribute significantly to the decomposition enthalpy in these explosives compared to the contributions from nitrate groups.

But as rolnor pointed out, more modern explosive compounds often do involve strained carbons, where the angle strain contributes to the decomposition enthalpy... as well as decreases stability.