Thermal Stability of a Eutectic Mixture of Bis(2,2‐dinitropropyl) Acetal and Formal: Part C. Kinetic Compensation Effect

Abstract

AbstractThe aging behavior of a eutectic mixture of bis(2,2‐dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70 °C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55 °C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO2 follows a 1st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre‐factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55 °C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55 °C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NOx, water, and HNO3 serve as catalysts to auto‐catalyze (kinetics beyond the 1st order) and further degrade NP. The effect of headspace volume on this auto‐catalytic process will be discussed.