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Author: Subject: Problem: RDX synthesis created nonflammable white powder
Chisholm
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shocked.gif posted on 4-6-2017 at 11:21
Problem: RDX synthesis created nonflammable white powder


So I performed the synthesis of RDX via the hexamine dinitrate in WFNA method, and in addition to a quantity of nitramine, I also have a white, powdery substance that is water-insoluble but also resists dissolving in acetone even at elevated temperatures.

My acid, ~80 grams, was rather yellow. Following advice I found here, I added small amounts of ammonium and urea nitrates to increase yield. Upon adding UNi, the hue of the acid darkened to an orange color and NOx evolution was apparent, so I blew air over the beaker until no more fumes appeared, then cooled the mixture in an ice bath to 15C, then added the HDN, maintaining sub-25 temperatures throughout. Well before addition of all 20 grams of HDN, the color of the acid had clarified to white and the gaseous evolution had mostly ceased. After full addition, I waited 15 minutes, heated the mixture to 55C for 15 minutes, then immediately poured the mixture into water, forming a white precipitate that was filtered, rinsed with water, treated with bicarbonate until dark green to litmus paper, then washed with 99% isopropanol and dried over a 24 hour period.

I placed the dry white powder in a beaker and added hot acetone that should have been sufficient to dissolve a large portion of the material if it were merely RDX. Almost no dissolution was apparent even at boiling temperatures.

To ascertain if there was even any RDX present, I filtered the hot acetone and added it dropwise onto a steel evaporating dish that was on a warm (100C) hotplate, letting each drop evaporate completely before adding the next so as to create a significant deposit that would not require extensive scraping to collect. Evaporating acetone left behind a white powdery substance that was visually indistinguishable from the undissolved material in the beaker, though after many additions the very edge of the white cake took on a bluish-green hue that I assume are polymerization products of the formaldehyde generated by the reaction.

Good news: Pouring hot acetone over the initial precipitate in the beaker, filtering the acetone into another beaker, then permitting it to evaporate over several days produced a crop of transparent crystals that, due to their structure, are unmistakably RDX.

The large lump of initial precipitate continues to yield RDX when heated with acetone. However, when a compressed flake of a few milligrams of the precipitate was separated with tweezers, placed on aluminium foil, and subjected to the direct heat of a gas grill lighter for upwards of 30 seconds, only moderate charring was seen, rather than the prompt ignition and horrible smell characteristic of hexamine dinitrate or the nearly residue-free combustion I hear is characteristic of RDX.

Wondering if the browned substance was baking soda with a coat of organics that had partially burned off (though the fact that I had washed the precipitate with water made this unlikely), I added a few drops of water to the aluminum foil, and while the tiny mass broke apart into black and brown flakes when agitated, there was no tell-tale change in refractive index that would indicate dissolution of a water-soluble salt.

Either I have been massively misinformed regarding RDX's ease of ignition and solubility in acetone at all temperatures, or some unidentifiable substance was produced by the reaction. If it is the later, I have no clue whatsoever what it could be.

Anyone else have any ideas? Anyone else experienced this?
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PHILOU Zrealone
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[*] posted on 5-6-2017 at 08:36


Your WFNA was thus a YFNA and after addition of NH4NO3 and UN it turned to be RFNA...

You may have uncompletely nitrated RDX...
CH2-NH-CH2 + NO2(+) --> CH2-N(NO2)-CH2 + H(+)
CH2-NH-CH2 + NO(+) --> CH2-N(NO)-CH2 + H(+)
CH2-NH-CH2 + HNO3 --> CH2-NH2(NO3)-CH2

The NH may turn into a nitramine, into a nitrosamine or into a nitrate salt...
You have 3 positions thus a lot of hybrid possibilities.

The urea may have lead to side reaction products related to keto-RDX but with the same uncompletely nitrated side product problems.

Also urea and hexamine may lead to urea-formol resinous (thermo hardening) products and soluble intermediaries...

[Edited on 5-6-2017 by PHILOU Zrealone]




PH Z (PHILOU Zrealone)

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Chisholm
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[*] posted on 5-6-2017 at 08:55


Quote: Originally posted by PHILOU Zrealone  
Your WFNA was thus a YFNA and after addition of NH4NO3 and UN it turned to be RFNA...

You may have uncompletely nitrated RDX...
CH2-NH-CH2 + NO2(+) --> CH2-N(NO2)-CH2 + H(+)
CH2-NH-CH2 + NO(+) --> CH2-N(NO)-CH2 + H(+)
CH2-NH-CH2 + HNO3 --> CH2-NH2(NO3)-CH2

The NH may turn into a nitramine, into a nitrosamine or into a nitrate salt...
You have 3 positions thus a lot of hybrid possibilities.

The urea may have lead to side reaction products related to keto-RDX but with the same uncompletely nitrated side product problems.

Also urea and hexamine may lead to urea-formol resinous (thermo hardening) products and soluble intermediaries...


But which of those, if any, resists ignition by prolonged direct contact with the flame of a gas grill lighter?
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PHILOU Zrealone
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[*] posted on 5-6-2017 at 12:56


Partially nitrated urea-formol-resin...looks like it



PH Z (PHILOU Zrealone)

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Chisholm
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[*] posted on 6-6-2017 at 10:55


The precipitate is bone-white and readily pulverized. Are you sure that would be resin? Also, the urea was likely destroyed by the nitrous acid present in the nitrating medium.

[Edited on 6-6-2017 by Chisholm]
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PHILOU Zrealone
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[*] posted on 6-6-2017 at 11:10


Quote: Originally posted by Chisholm  
The precipitate is bone-white and readily pulverized. Are you sure that would be resin? Also, the urea was likely destroyed by the nitrous acid present in the nitrating medium.

[Edited on 6-6-2017 by Chisholm]

Depends stongly on how much you did actually put into reaction...it is not stated into your initial post.
The stange thing is that Urea prevents NxOy by destroying it and leading to CO2, N2 and H2O...

Uncontroled urea-formol processed is indeed kind of porous white brittle unsoluble stuff...




PH Z (PHILOU Zrealone)

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