Salts of Bis furoxano -2-nitrophenol

The sodium salt can be prepared in the same way as the potassium salt. It appears in an anhydrous form (as opposed to the Norris method [50]), which is, however, highly hygroscopic and rapidly absorbs water on standing (18 % water uptake on standing at 25 °C for 5 h in humid conditions 92 % RH). The potassium salt did not demonstrate a tendency to adsorb water even under these conditions [46]. 

The potassium salt of 7-hydroxy-4,6-dinitrobenzofuroxan is proposed as a low toxicity LS replacement with application in hot-wire igniter systems [51, 53]. 

The salts of bis(furoxano)-2-nitrophenol (BFNP, hydroxynitrobenzodifuroxan) have been recently reported by Fronabarger et al. [54] and Sitzmann et al. [55] 

Alkaline salts of bis(furoxano)-2-nitrophenol are red-brown while the guanidinium salt is light yellow. Fronabarger et al. assume that the red-brown color is due to structure I. It is supported by the fact that when yellow crystals of the guanidinium salt (type II structure) are dissolved in dimethyl sulfoxide the color of the solution is red-brown, the same as for the other salts. The content of both forms of the guanidinium salt in solution was proved by NMR analysis. Removing solvent leads to a light yellow residue [2]. 

Density of the potassium salt is 2.106 g cm [55] and it explodes at about 165 °C on heating. The sodium salt forms a monohydrate and is highly water soluble [2, 55]. The rubidium salt has properties similar to the potassium salt it forms red-brown crystals with density 2.399 g cm and ignition temperature 

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The salts of bis(furoxano)-2-nitrophenol can be prepared by reaction of bis (furoxano)nitrophenol with the relevant carbonate, acetate, or hydroxide in aqueous solution [54—56]. 

Alkaline salts of bis(furoxano)-2-nitrophenol (primarily KBFNP) were proposed as heavy metal-free primary explosives. Even the most promising candidate— KBFNP—exhibits low thermal stability at temperatures over 100 °C and even more importantly it has a very low performance in comparison with LA. As an unsuitable LA replacement, it may find some use in igniting compositions replacing LS. KBFNP has been also investigated for use in actuators or micro-propulsion systems [54],... 

The preparation of bis(furoxano)-2-nitrophenol salts is a four-step procedure developed by Fronabarger and his collaborators. It is based on formation of a diazidotri-nitrobenzene intermediate containing a hydrolysable group. This intermediate gives bis(furoxano)-2-nitrophenol by hydrolysis [54]. 

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