Thermal Stability of Several Organic Hydroxylamine Derivatives and a Broader Look at Explosive Hazard Identification

Organic derivatives of hydroxylamine are important reagents in modern chemistry, but their thermal stability and related hazards have not yet been systematically studied. In the present study, we report a detailed thermal analysis of N-hydroxysuccinimide (NHS), N-hydroxyphthalimide (NHPI), 1,4-piperazine diol (PipzDiol), 1,3,5-trihydroxy-1,3,5-triazinan-1-ium chloride (formaldoxime trimer hydrochloride, TFO·HCl), and tris-oxime TRISOXH3. Then, we suggest the effective kinetic parameters and mechanisms of thermal decomposition. All these NOH-containing chemicals exhibit the exothermic decomposition when examined under conditions that retard material vaporization (such as DSC at elevated pressure or in hermetic crucibles). The application of Yoshida-type rules points to a certain hazard associated with TFO·HCl, TRISOXH3, and PipzDiol. Small-scale mechanical sensitivity testing validated the DSC-based hypothesis: TFO·HCl explodes at certain drop energies, and two other species decompose under impact. The standard drop energies corresponding to 50% probability of initiation are within 14–26 J. Overall, the reactive chemistry of the analyzed hydroxylamines may result in certain risks when they are stimulated by temperature or impact. Even for well-known reagents such as NHS, the amount of heat liberated in the course of decomposition is considerable (about 1300 J g–1). 1,3,5-Trihydroxy-1,3,5-triazinan-1-ium chloride by the amount of decomposition enthalpy (2200 ± 300 J g–1) and the level of the impact sensitivity (16 ± 5 J) can be compared with explosives, but it is less thermally stable, decomposing above 100 °C. The calculation of virtual detonation performance of this salt shows much higher stored energy as compared to other studied hydroxylamines. We propose the calculation of the detonation parameters for screened compounds as an alternative way of explosive hazard identification.