Wallace et al reported azoxytriazolone

Wallace et al. reported azoxytriazolone (AZTO) (20) and azotriazolone (azoTO) (21) as insensitive high nitrogen compounds of energetic materials (Fig. 9) [67]. AZTO and azoTO were synthesized from NTO electrochemically, as mentioned above, and characterized by a range of techniques and compared to existing insensitive high explosives. AZTO, produced via electrolysis of aqueous NTO solutions, shows similar sensitiveness to NTO in most tests, but has better thermal stability. During the synthesis of AZTO, another new species, azotriazolone (azoTO), is also produced [42]. AzoTO displays higher thermal and impact stability than AZTO but is more sensitive to electrostatic discharge. AZTO sensitiveness is not affected by the presence of azoTO (formed concomitantly during synthesis) at levels of <20%. Crude samples and recrystallized samples react similarly in the tests performed. The ease of synthesis, low sensitiveness and moderate CGP41251 output and the structure and oxygen balance of AZTO suggest that AZTO may be an economical and environmentally-friendly addition to the existing range of IHE. Azoxytriazolone (AZTO) precipitates from solution in good yield [42]. Thus, the formation of solid AZTO from waste NTO solutions could prove to be a very economical method of remediation. AzoTO is present at levels of 10–20% in typical batches of AZTO and cannot be removed by recrystallization. The amount of azoTO can be limited to <5% by use of lower cell temperature, which also increases the yield of AZTO from the reaction. AzoTO can be prepared in pure form via electrochemical reduction of AZTO [42]. They carried out small-scale tests on several different samples. Since typical samples of AZTO contain around 15% azoTO as a side product, it was crucial to determine the effect of azoTO on the behavior of AZTO. Tests were carried out on three sets of samples: typical AZTO samples with approximately 15% azoTO, AZTO samples with low azoTO content (<5%), and samples of pure azoTO. AZTO samples also might contain traces (<3%) of hydrazotriazolone and/or aminotriazolone [42] (these can be removed by recrystallization from DMSO–water). The authors said that this process causes the proportion of azotriazolone to increase slightly and leaves traces of DMSO even after the samples have been washed many times with water and dried in vacuum at 100 °C for 48 h. The recrystallized samples in the study were also tested to assess the effect of minor impurities and residual DMSO on the sensitiveness of the samples. The samples were tested for sensitiveness to impact, friction, electrostatic discharge (ESD). The results are compared with data for established materials included for comparison. AZTO behaved similarly to NTO in impact and ESD tests and showed greater stability in the friction tests. On the other hand, AzoTO displayed greater sensitiveness to ESD than AZTO, but AZTO samples containing typical amounts of azoTO (<20%) were not found to display increased sensitiveness to ESD. However, the tests indicated that a higher azo content of 30% was sufficient to increase the ESD threshold of AZTO samples. On the other hand, azoTO was found to be much less sensitive to impact than either NTO or AZTO. No measurable differences were observed in sensitiveness between AZTO samples synthesized at low temperature and synthesized at room temperature. There were also no observable differences between samples that had been recrystallized from DMSO–water and those that had simply been washed with water. AZTO is soluble in DMSO but has very poor solubility in all other organic solvents, including DMF, acetone, methanol, ethanol and acetonitrile. Also the solubility in water is very low, measured at 20 ± 5 mg L−1 at 18–19 °C. The investigation reveals that AZTO has good solubility (and stability) in neat sulfuric acid, from which it can be precipitated via addition of the solution into water. The material also dissolves readily in aqueous alkali due to deprotonation of the triazole ring(s).