Han Gao,Xiaolu Yao,Ming Huang,Jialin Cai,Zhirong Suo,Guan Luo
In this study, a self-assembled spherical shell and porous spherical structures of 3,3′-diamino-4,4′-azoxyfurazan (DAAF) were fabricated by a simple surfactant-induced and a solvent-induced method, respectively. Scanning electron microscopy (SEM) was employed to characterize their morphology. The results of X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy indicated that the crystal and molecular structures of both products remained unchanged when compared with the case of raw DAAF. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to characterize the thermal behavior of the as-prepared crystals, and the related thermodynamic parameters were calculated. Finally, the self-assembly mechanism has been discussed.
Jian-Bo Chen,Xueyan Zhao,Zhenqi Zhang,Ya Chen,Xiaolin Fu,Yu Liu
Recently, 3,3-diamino-4,4-azoxyfurazan (DAAF) as one of most promising energetic furazan compounds has been widely studied because of its excellent explosive performances. Nowadays, the Oxone oxidation method is regarded as a main pathway to synthesize DAAF. However, several unknown impurities are yielded when the Oxone method is used to prepare DAAF. The identification of DAAF’s impurities is beneficial to optimize synthetic route of DAAF and then improve its purity. In this study, chemical structures of DAAF and its main impurities were analyzed by developing an unknown analysis workflow based on ultrahigh-performance liquid chromatography-tandem diode array detector -tandem high resolution mass spectrometry (UHPLC-DAD-HRMS). They were fully separated by UHPLC after the optimization of chromatographic conditions. HRMS based on a Q-Orbitrap system was performed to elucidate chemical structure of the impurities by determining exact mass of the impurities and their MS/MS fragments. Besides DAAF, eight unknown impurities were detected under negative ion mode ([M-H] - ) of HRMS with a heated electrospray ionization. Comprehensive analysis of UHPLC-DAD-HRMS provided more information including the retention time, UV–Vis spectrum, elementary composition and MS/MS fragments, and then possible structures of the impurities were proposed in this work. Further, the ion at m / z 211.0328, impurity I and impurity V were confirmed to be DAAF, DAF and DAAzF, respectively, through 1 H NMR and 13 C NMR after synthesizing their reference materials. In addition, the source of these impurities during the synthesis of DAAF has been analyzed. The impurities were originated from the precursor, the intermediate and byproduct of preparing DAAF through the hydrazine, the isomerism and the nitrosation.
Since the traditional approaches for 3,3’-diamino-4,4’-azofurazan (DAAF) synthesis are not environment-friendly and economical enough, the development of green and low-cost approaches for the synthesis of DAAF is valuable and significant. Herein, the electrochemical synthesis of DAAF from the oxidation of 3 4-diaminofurazan (DAF) was studied in different electrode and electrolyte systems. It was found that the pH of alkaline aqueous electrolyte, the solvent of electrolyte and electrode play important role in DAF oxidation into DAAF. In an electrochemical cell with graphite sheet anode, Pt wire cathode and DAF/ n Bu 4 NBF 4 /acetonitrile electrolyte, the optimal DAAF yield of 63% and faradic efficiency above 60% (at 1.80 V vs. Ag/AgCl) were achieved. Mechanism investigations revealed that the electrochemical synthesis of DAAF in such an electrochemical cell is originated from the direct oxidation of DAF on graphite anode, not involving radical pathway. Graphical
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