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Author: Subject: Nitration of hexamine via patent 3981975?
j_smith
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[*] posted on 27-11-2006 at 17:58
Nitration of hexamine via patent 3981975?


Has anyone ever tried Coon's method of nitration using the methylene chloride raffinate as he proposes in his patent?
He claims it is a "useful nitrating agent" and gives a couple of examples in his patent, but really how successful is this proceedure?

It seems almost too simple to be true!
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Sickman
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[*] posted on 27-11-2006 at 22:29


Methylene chloride seems to be a viable option for preparing an anhydrous nitric acid.

There is at least three problems I see and they all deal with economics.

First, I have never seen pure methylene chloride for sale OTC. Which is the first problem, but may not be a problem for you, but make sure that it is pure!

Second, once the anhydrous nitric acid is obtained by distillation in accordance with US3981975, a great excess of nitric acid to hexamine is required for the proper nitration to the trinitrate, 550 grams 100% acid to 50 grams of hexamine and the yield from this is only 68% at best. Temperature control is essential.

Thirdly, after spending all that money on chemicals and distillation apparatus, I'm sure you will want to recover as much nitric acid after the nitration as possible, however "the formaldehyde which is liberated by the reaction tends to be oxidized by the nitric acid if the mixture is allowed to stand or is warmed. It remains in the spent acid after drowning and interferes with the recovery of nitric acid from it."

To sum it up, hexamine is very difficult to nitrate completly to RDX compared to most other explosive nitrations. If you have the money and access to materials you can make and purify RDX in a very low yield and at a very high cost to yield ratio, for example, compared to PETN's 95%+ yield and a much smaller acid to powder ratio.
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Boomer
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[*] posted on 28-11-2006 at 00:11


Have you thought about combining this with the HDN route? (It is more acid efficient anyway.) You might dilute the spent acid only to say 40%, which will precipitate most of the RDX, while being low enough to prevent said decomposition/runaway.

After filtering, the 40% stuff could be sample-tritrated (to get %) and mixed with conc. hexamin solution to yield HDN, this way you get around distilling the unstable mix for nitric recovery.

BTW via HDN my RDX yield is consistently above 70%, though the 82% I was unable to reproduce. I wish I had half that yield for other precursors with the nitro group somewhere (nitroethane, nitrostyrenes...)! :P
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j_smith
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[*] posted on 28-11-2006 at 03:38


Both good suggestions, but...

The question is, has anyone tried nitrating hexamine using the methylene chloride raffinate as Coon proposes in his patent?

And yes, I have plenty of pure MC.
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Sickman
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[*] posted on 29-11-2006 at 22:33


I have not used that method of nitration before. However I'd like to speculate based on example 5 of the patent which mentions using the MC/ANA mix to nitrate anthracene. As you can see it only resulted in the dinitrate. Not to mention only a 78% yield for a dinitrate.

I think that if the methylene chloride were first boiled out, that it may have resulted in the trinitrate or if there is trouble with that direct a method, the anthracene may first be sulphonated and then treated with anyhydrous nitric acid to replace the sulphonated groups with nitro groups.

It just seems logical to me that diluting anhydrous nitric acid with methylene chloride reduces the surface area of the nitric acid and thereby causing a less effeciant nitrating agent.

[Edited on 30-11-2006 by Sickman]
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[*] posted on 29-11-2006 at 22:56


Does this surface area change occur because of a density change or because the nitric acid is misicible with the dichlormethane?



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j_smith
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[*] posted on 30-11-2006 at 06:19


Yes, that is along the lines of my thoughts, too.
Either the nitration wouldn't be complete, or the process would take a longer time to completion. After all, the acid is diluted.

I may just have to give this a shot and see where it goes...when I get some spare time :)
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[*] posted on 30-11-2006 at 07:07


Seems resonable. Even though the acid/solvent-mix is anhydrous, the nitric acid-consentration is lower than in a pure sample. It should be comparable to the nitrate/sulphuric acid method that I have seen from time to time.

Even so, it is an intriguing approach to the topic. For some syntheses it might be quite possible to use the mixture directly, and if not it still seems like a useful route to ANA.
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