Thermal decomposition of energetic materials 63. Surface reaction zone chemistry of simulated burning 1,3,5,5-tetranitrohexahydropyrimidine (DNNC or TNDA) compared to RDX

Liquid state thermochemical decomposition of neat 1,3,5,5-tetranitrohexahydropyrimidine (DNNC) and its DNNC-d2, DNNC-d4, DNNC-d6 structural isotopomers: Mechanistic entrance into the DNNC molecule

“…Related cyclic nitramines RDX and HMX melt, or undergo liquefaction, with decomposition rapidly enough that their heat of fusion cannot be obtained. Additionally, DNNC and RDX structural variation affects thermochemical properties related to rapid pyrolysis and simulated combustion behavior [4,38].…”

“…The partially deuterium-labeled DNNC-d 2 and DNNC-d 4 compounds were synthesized using an identical Mannich condensation reaction procedure, and scaled as needed, by employing the appropriate choice of unlabeled or deuteriumlabeled 2,2-dinitropropane-1,3-diol (ADIOL and ADIOL-d 4 [33]. Within the accuracy and precision of 1 H NMR integration values, the intermediate DBNP-d 2 reflected an incorporation of 2.2 methylene deuterium atoms; DBNP-d 4 incorporated 4.0 methylene deuterium atoms, and 5.9 methylene deuterium atoms were incorporated into the DBNP-d 6 molecule relative to the two unlabeled tert-butyl groups substituted on the ring nitrogen atoms at the 1-and 3-ring positions.…”

“…Proton NMR integrations of the two different methylene groups (δ 6.30 C-2 and δ 5.47 C-4 and C-6) for both DNNC-d 4 and DNNC-d 2 remained in a 1:2 integration ratio, respectively, indicating a random distribution of the labeled CD 2 deuterium-labeled methylene groups occurred at all three C-2, C-4, and C-6 ring positions. In spite of this randomized CD 2 methylene distribution, relevant mechanistic information was obtained by comparing DNNC, DNNC-d 2 , DNNC-d 4 , and DNNC-d 6 IDSC isotopomer induction times and rate constants.…”

“…For example, isothermal differential scanning calorimetry (IDSC) global kinetics rate constants, determined for the solid state thermochemical decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), accurately predict the 354 • C experimentally determined critical temperature which initiates a thermal explosion event [3]. The condensed phase neat thermochemical decomposition process an energetic compound follows is primarily a complex mechanistic set of interacting intermolecular bimolecular reactions [4] with some degree of intramolecular unimolecular character. Generally, two key chemical bond ruptures occur General thermochemical decomposition process schematic representation and the KDIE measurement context [13].…”

“…Given the importance of this high-energy rate-controlling mechanistic feature, the thermochemical decomposition of neat liquid DNNC, and its three isotopomers, DNNC-d 6 , DNNC-d 4 , and DNNC-d 2 , was investigated by isothermal DSC to determine the ratecontrolling homolytic bond rupture and its location in the DNNC molecular structure. Similarities and differences between this neat liquid state DNNC thermochemical decomposition process, and the previously reported mechanistic solid state DNNC thermochemical decomposition investigation [2], also are compared.…”