2
$\begingroup$

When reading about TNT (trinitrotoluene), I noticed that the aromatic ring has still 2 carbon atoms left for two more possible nitro groups ($\ce{−NO2}$), which would get you tetra- or pentanitrotoluene.

Unsubstituted carbon atoms in TNT

The amount of available oxygen in TNT is not enough for a complete oxidation to water and carbon dioxide, this is obvious when looking at a possible reaction: $$\ce{2 C7H5N3O6 -> 3 N2 + \mathbf{5\,H_2} + 12 CO + \textbf{2 C}}$$ Thus tetra- and pentanitrotoluene should be better explosives than TNT, because they both provide more oxygen than TNT. Why they were never popular? Are they harder to fabricate than TNT, can you nitrify them from TNT? Are they maybe unstable?

$\endgroup$
6
  • 4
    $\begingroup$ The synthesis is probably neither feasible not effective enough. You'll get better bang for fewer bucks. $\endgroup$ Commented Dec 27, 2020 at 16:20
  • 7
    $\begingroup$ Pentanitrotoluen has been prepared patents.google.com/patent/US4451681A/en You have to balance their explosive power against the difficulty of production and handling $\endgroup$
    – Waylander
    Commented Dec 27, 2020 at 16:27
  • 2
    $\begingroup$ Keep in mind that octanitrocubane would have ideal stoichiometry but is much harder and more expensive to synthesize .. and ironically seems to have lower crystal density. Having talked to a few explosives chemists, there's a lot unknown (even beyond the "we're not talking" bits). $\endgroup$ Commented Dec 27, 2020 at 20:42
  • $\begingroup$ On more serious note, yes they're obviously unstable and I wonder why these guys^ bothered with patent. $\endgroup$
    – Mithoron
    Commented Dec 27, 2020 at 20:48
  • 1
    $\begingroup$ Read up on steric inhibition of resonance and you'll get some insight. $\endgroup$
    – Mithoron
    Commented Dec 28, 2020 at 20:02

1 Answer 1

1
$\begingroup$

Tetranitrotoluene and pentanitrotoluene is defintely possible but the synthesis is not straightforward.

Isomeric tetranitrotoluenes were prepared through peroxodisulfuric oxidation of trinitrotoluidine. Another method include hypophosphorous reduction of diazonium salt derived tetranitrotoluidine. See ref. 1 for more details.

Pentanitrotoluene is prepared by preparing an aminodinitrotoluene from a precursor of either TNT or 2,5-dinitro-3-methylbenzoic acid, nitrating the aminodinitrotoluene to produce a nitramine intermediate, converting the nitramine intermediate to an aminotetranitrotoluene and oxidizing the aminotetranitrotoluene with peroxydisulfuric acid to pentanitrotoluene.

Now, why TNT is more popular than tetra- and penta- derivates?

  1. First of all, preparing is TNT is easier and more direct. Even it can be prepared through laboratory reagents in small scales. Tetra- and penta- derivative is far more difficult to synthesize, requires more expensive reagents and the reaction is hard to control
  2. It is comparatively insensitive to shock and friction, with reduced risk of accidental detonation. Compare it with the tetra- and penta- derivative, TNT is far more stable. More nitro- groups added, more is the ring strain and steric inhibition.

In similar vein, picric acid is more popular than its tetra- and penta- derivatives.

References:

  1. Synthesis of Tetranitrotoluenes, Arnold T. Nielsen, Stephen L. Christian, Andrew P. Chafin, and William S. Wilson, The Journal of Organic Chemistry 1994 59 (7), 1714-1718, DOI: 10.1021/jo00086a020
  2. *PATENTS, *PETN, EXPLOSIVES, SYNTHESIS(CHEMISTRY), DNT, TNT, NITRAMINES, NITRATION, OXIDATION, INDUSTRIAL PRODUCTION, COST EFFECTIVENESS, Atkins,Ronald L.; Hollins,Richard A.; Norris,William P.; Nielsen,Arnold T., DEPARTMENT OF THE NAVY, WASHINGTON DC, 1984 (link)
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.