A STUDY OF THE SENSITIVITY AND DECOMPOSITION OF 1,3,5-TRINITRO-2-OXO-1,3,5-TRIAZACYCLO-HEXANE

The thermal decomposition and thermal stability of 1,3,5-trinitro- 2-o xo-1,3,5-triazacyclohexane (keto-RDX or K-6) was studied. The keto-RDX synthesis is described, mass spectra (electron impact (70 eV) and che mical ionization) similar to RDX spectra registered under identical co nditions are presented, and mass spectroscopy fragmentation paths are proposed. The LI-MS (laser induced/mass spectroscopic) results imply t hat the first step in the decomposition of keto-RDX is the elimination of NO2 or HONO and subsequent breakdown of the triazacyclohexane ring . The thermal stability, activation energy (E(a) = 140 kJ mol(-1)), an d frequency factor (K-0 = 9 x 10(9) s(-1)) in the temperature interval 90-120 degrees C were measured using chemiluminescence (NO detection only). The activation energy was also determined from DSC data using t he ASTM method E 698-79, and was found to be 280 kJ mol(-1) with a fre quency factor of 7.0 x 10(29) s(-1) in the temperature interval 175-20 0 degrees C. Microcalorimetry, drop-weight test, friction test, and ig nition temperature (Wood's metal hath) measurements were also conducte d. Quantum mechanical calculations (semi-empirical MNDO method with PM 3 set at the unrestricted Hartree-Fock level) were conducted to correl ate the sensitivity and thermal decomposition with those of RDX. No si gnificant differences in bond-breaking energies for RDX and keto-RDX w ere found. Conclusions drawn from the experiments are that the decompo sition of keto-RDX is auto-catalytic, and that the sensitivity of keto -RDX is not connected with the initial bond-breaking step. More than o ne method for measuring the risk involved in handling an explosive is necessary since the sensitivity depends on different stages in the dec omposition.