Study of the synthesis mechanism of 4-amino-3,5-dimethyl pyrazole by fibre optic in-line FT-IR spectroscopy combined with independent component analysis

Abstract

The application of Fourier transform infrared (FT-IR) spectroscopy for in-line monitoring of the synthesis process of 4-amino-3,5-dimethyl pyrazole is described. The obtained data matrix of IR was analyzed by a well known chemometric method, independent component analysis (ICA), which determined the concentration profiles and the spectra of the reactant, intermediates and product. The geometric configurations of the intermediates were fully optimized and the vibrational frequencies computed at the density functional theory (DFT) B3LYP/6-31G level of theory. The computational results by the ICA method are in good agreement with those by the quantum chemical calculation method, which demonstrated the reliability of the proposed ICA method. The possible synthesis mechanism was deduced, and the results indicated that ICA combined with in-line FT-IR spectroscopy can be used to study the synthesis mechanism of 4-amino-3,5-dimethyl pyrazole successfully.