nematic
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Facile and high yield diaminoazoxyfurazan and diaminoazofuroxan
This will probably be of great interest to Axt, and of tangential interest to Engager.
It is well known that 3,4-diaminofurazan will form 3,3'-diamino-4,4'-azo{xy}furazan on oxidation with specific reagents. What seems to be common
knowledge (e.g. http://www.sciencemadness.org/talk/viewthread.php?tid=5813) is that the azoxyfurazan will form in cold aqueous H2O2/H2SO4. What is problematic
with this synthesis is its low yield (57%), the use of concentrated sulfuric acid and careful temperature control.
What I discovered last night is that there is another route, much simpler to perform and much higher yielding. Ladies and gentlemen, please turn your
attention to a recent patent application: http://www.freepatentsonline.com/20090306355.pdf
The best yielding variation of this synthesis is given in example 15:
An aqueous solution of DAF (150 g, 1.5 mol) and sodium bicarbonate (378.2 g, 4.5 mol) in water (about 9 liters) was prepared at room temperature
(about 22 deg C) in a 22-liter non-jacketed flask. Oxone (922.5 g, 1.5 mol) was added in three portions of about 300 g each to the solution. After
stirring for about 2 h the pH was measured at 6.32. Additional sodium bicarbonate (378 g, 4.5 mol) was added resulting in a pH of 7.36. Additional
Oxone (922.6 g, 1.5 mol) was added, resulting in a pH of 6.98. Stirring was continued for about another 2 h, after which the pH was measured at 6.78.
The solid product that precipitated from the solution was filtered and washed with water, yielding 134.3 g (89.55%) of essentially
pure DAAF. The mean particle size of DAAF was determined to be 41 um.
As can be seen, the relatively very high yielding synth uses a very simple protocol, requiring 2 mols oxone per 1 mol DAF and only rudimentary pH
control with sodium bicarbonate. I have a feeling it might be minimally improved, at least to eliminate the second addition of bicarbonate, by
employing a buffer solution. Oxone (potassium peroxomonosulfate, 2KHSO5.KHSO4.K2SO4) is relatively cheap and unwatched, non-toxic, non corrosive and
easy to use.
A second interesting synth in this patent application can be seen in example 23:
DAF (0.5 g, 5 mmol) was added to an aqueous solution of sodium bicarbonate (0.84 g, 10 mmol) and 10 ml of water at room temperatur (about 23 deg C). A
solution of 5% NaOCl (i.e. household bleach, 15 ml) was then added slowly over 15 minutes to the DAF/sodium bicarb mixture. The
reaction was then stirred an additional 15 minutes. The orange solid was filtered from the solution and washed with cold water and dried. Analysis of
the solid showed that the product was not DAAF, but instead was 3,3'-diamino-4,4'-azofurazan. The yield was 90%
Another super-simple and high yielding protocol, this time it's totally kitchen chemistry.
Interesting question that these two methods raises is: can these be used on 5-aminotetrazole to form, respectively, azotetrazole with NaOCl (instead
of the usual inelegant and pricey oxidation with KMnO4) and - perhaps! - azoxytetrazole with oxone? Is azoxytetrazole even known in the literature? My
search turned exactly zero results. If it can be prepared this way and is stable (it should be!), it should be quite a powerful explosive that easily
forms salts, just as the azotetrazole forms them.
My reason for expecting these methods to carry over to aminotetrazole is that the tetrazole ring is chemically similar to the furazan ring - both are
very electron deficient and generally very stable to chemical transformations. If someone has some aminotetrazole on hand, these two ideas might be
very much worth trying!
BTW, hello to all. I'm a long time reader hoping to bring in here something of my own here from time to time.
[Edited on 22-8-2010 by nematic]
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nematic
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Another idea that just popped in my mind is trying to synthesize 3,3'-dinitro-4,4'-azofurazan from the diamino derivative using a method analogous to
what is used on the diaminoazoxyfurazan (H2O2/ammonium persulfate/conc H2SO4). The synth might not exactly be very efficient (the original has a 60%
yield), but the product would probably be a VERY powerful explosive (HMX class or thereabouts), not as powerful as the azoxy (which is comparable to
HNIW), but maybe more stable. The dinitroazofurazan is known in the literature (see eg US 6388087), but I have never seen any energetic properties of
this compound.
The hypochlorite method used on 1-methyl-5-aminotetrazole works quite well to give 1,1'-dimethyl-5,5'-azotetrazole, as can be seen here: http://www.freepatentsonline.com/3925086.pdf (see ex. 5) The protocol is simple and actually involves boiling the aqueous
hypochlorite-aminotetrazole solution. Yield is not stellar, but it works allright. Works on 2-methyl-5-aminotetrazole, 1-allyl-5-aminotetrazole, and
2-allyl-5-aminotetrazole as well.
[Edited on 22-8-2010 by nematic]
[Edited on 22-8-2010 by nematic]
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Anders2
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The reason that the yields with NaOCl is so good is probably because nitrogenous anions are formed (at least in equilibrium), and these anions are
much more suscepible to oxidation than the same compound that is either neutral, or has accepted a proton from an acid. An analogy is SO2 , which is
very difficult to oxidize, but under basic conditions, the sulfite formed easily is oxidized to sulfate, unfortunately SO3 is too acidic for the
sulfate to revert to it. While NH4OH can be oxidized by H2O2, NH4Cl is inert to the oxidizer, showing that acidic conditions protect amines from
oxidation.
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