Thermal Stability Of A Eutectic Mixture Of Bis(2,2-Dinitropropyl) Acetal And Formal: Part C. Kinetic Compensation Effect

The 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 degrees 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 degrees C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO(2)follows a 1(st)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 degrees C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55 degrees C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NOx, water, and HNO(3)serve as catalysts to auto-catalyze (kinetics beyond the 1(st)order) to further degrade NP. The effect of headspace volume on this auto-catalytic process will be discussed.