In situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy combined with non-negative matrix factorization for investigating the synthesis reaction mechanism of 3-amino-4-amino-oxime furazan

In situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy combined with a non-negative matrix factorization (NMF) algorithm was proposed to elucidate the synthesis reaction mechanism of 3-amino-4-amino-oxime furazan (AAOF). An in situ ATR-FTIR fiber was used to monitor the reaction process, and discrete wavelet transform (DWT) was used to preprocess the IR spectra. A subspace comparison method (SCM) was employed to determine the optimal number of components; then the NMF algorithm was applied to decompose the optimal IR spectra into spectral and concentration profiles of the reactants, intermediates and product. Quantum mechanical calculations based on density functional theory (DFT) were applied to simulate the vibrational spectra of the intermediates at the B3LYP/6-31+G(d,p) level, and the calculated spectra were compared to the decomposed spectra of the intermediates involved in the synthesis. The spectra obtained by the NMF algorithm were consistent with quantum mechanical calculations. Finally, a reliable mechanism for the synthesis of AAOF was proposed based on the shifts in the IR bands of the reactants, intermediates and product. The results indicate that the ATR-FTIR technique combined with an NMF algorithm can be used to explore the mechanism of AAOF formation.