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Author: Subject: Cyclization of Diaminoglyoxime to Diaminofurazan, unsure of synthesis.
Rhodanide
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[*] posted on 20-9-2019 at 12:02
Cyclization of Diaminoglyoxime to Diaminofurazan, unsure of synthesis.


Hi all,
I've successfully made what I presume to be Glyoxime and am looking to continue on to eventually make Diaminoazoxyfurazan. According to Axt's old post about Furazans and the related compounds, Diaminoglyoxime must be heated with aqueous KOH in a sealed steel reactor. Uhh, what? Not only do I not have a steel reactor available to me, but putting potentially energetic compounds in a steel vessel and heating it on an oil bath seems like something I'd like to avoid. What I want to know is, if the whole steel reactor is necessary, and can I just get by with using normal glassware at normal atmospheric pressure? Or even better, is there a different pathway to cyclize DAG to DAF? Please let me know. If I could I'd ask Axt himself, but who knows where that guy has been all these years.




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[*] posted on 20-9-2019 at 12:06


I'd also be happy with a synthesis of just Furazan from Glyoxime. I can't find an easy synth anywhere really.



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[*] posted on 24-9-2019 at 10:51


Diaminofurazan is not an energetic material, and an aqueous solution is definitely not an explosive hazard.
According to Axt's paper, the reaction needs to be performed at 180°C. The vapour pressure of water at that temperature is 10 bar, so you understand why steel is used and not regular glassware.




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Microtek
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[*] posted on 25-9-2019 at 03:16


I've done this synthesis in the past using the classical procedure. As Dornier says, the cyclization happens at a reasonable rate only around 170-180C. If the reaction medium is water, then obviously the pressure needs to be quite high, hence the autoclave.
I have read a paper that uses ethylene glycol instead of water and is therefore able to conduct the reaction at normal atmospheric pressure. I have tried that procedure once, but had a thermal runaway and moved on to other projects without exploring further.

I think you should look into the ethylene glycol mediated procedure if you wish to avoid the pressure vessel. However, a pressure vessel can be constructed fairly easily from a steel water pipe with caps screwed on both ends. If the threads are lubricated with a sufficient amount of silicone sealant, the silicone quickly polymerizes as the temperature rises, and the caps can still be screwed off after the reaction. You need to be quite sure of your temperature control, since the pressure rises quickly if you go much beyond 180C.
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[*] posted on 25-9-2019 at 05:09


Depending on the scale you're running at, pipes can be incredibly strong. At 200°C, water has a vapor pressure around 210 psi, and at 300°C about 1250 psi. There are a variety of pressure relief fittings using stainless burst discs available which could leave you with a mess instead of a bomb if something goes wrong. However, sch 80 stainless pipe is quite strong, handling the vapor pressure and temperature of water at 316°C/1600psi up to 2" diameter. Remember that burst pressure is much higher than working pressure since working pressure is designed to also handle transients brought about by fluid flow at the working pressure.

https://www.mcmaster.com/burst-discs
https://www.engineeringtoolbox.com/stainless-steel-pipes-pre...
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[*] posted on 25-9-2019 at 08:03


Yes, as far as I could tell, I was pretty far from any potential catastrophic failures, and I had mapped the behaviour of the kitchen oven to make sure it didn't overshoot. It was still a nerve wracking experience.
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