Development of monitoring software combined infrared spectra with multivariate curve resolution-alternating least squares (MCR-ALS): Tracking the dynamic synthesis process of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT)

The monitoring and analysis of chemical reaction processes are essential for improving reaction efficiency, optimizing production conditions, and ensuring product quality. Infrared spectroscopy, as a non-destructive and real-time analytical technique, provides dynamic insights into the evolution of component concentrations within reaction systems. In this study, the monitoring software was developed by combining infrared spectra with multivariate curve resolution-alternating least squares (MCR-ALS) to dynamically track complex chemical reactions. Using the synthesis of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT) as a case study, the concentration profiles and pure spectra of the reactant hexamethylenetetramine (HMTA), the esterified intermediate (3-acetoxymethyl-7-nitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane), and the product (DPT) were successfully resolved. Computed infrared spectra for HMTA and DPT showed high similarity to measured spectra, with similarity scores of 0.937 and 0.915, respectively. MCR-ALS analysis allowed deduction of the intermediate structure and proposal of the DPT synthesis mechanism, consistent with prior reports and validating the accuracy of the method. Kinetic modeling revealed a three-stage reaction pathway following an A → B → C model, where A, B, and C correspond to HMTA, the esterified intermediate, and DPT, respectively. The process follows first-order kinetics with rate constants of k₁ = 0.095 min⁻¹ and k₂ = 0.00419 min⁻¹. Overall, this study demonstrates the potential of the developed software for monitoring complex reaction systems, supporting process optimization, quality control, and risk management.