Thermal decomposition of energetic materials. 4. Deuterium isotope effects and isotopic scrambling (H/D, {sup 13}C/{sup 18}O, {sup 14}N/{sup 15}N) in condensed-phase deomposition of 1,3,5-trinitrohexahydro-s-triazine
- Sandia National Labs., Livermore, CA (United States)
- Army Armament Research, Development, and Engineering Center, Dover, NJ (United States)
The inter-vs intramolecular origin of the products formed in the thermal decomposition of 1,3,5-trinitrohexahydro-s-triazine (RDX) has been traced by isotopic crossover experiments using mixtures of differently labeled analogues of RDX. The isotopic analogues of RDX used in the experiments include {sup 2}H, {sup 13}C, {sup 15}N, and {sup 18}O. The fraction of isotopic scrambling and the extent of the deuterium kinetic isotope effect (DKIE) are reported for the different thermal decomposition products. Isotopic scrambling is not observed for the N-N bond in N{sub 2}O and only in small amounts (7%) in the C-H bonds in CH{sub 2}O, consistent with a mechanism of their formation through methylene nitramine precursors. A product, oxy-s-triazine (OST, C{sub 3}H{sub 3}N{sub 3}O) does not undergo isotopic scrambling in H/D, {sup 14}N/{sup 15}N, or {sup 13}C/{sup 18}O experiments, and its rate of formation exhibits a DKIE of 1.5. These results are consistent with the formation of OST via unimolecular decomposition of RDX. Another product, 1-nitroso-3,5-dinitrohexahydro-s-triazine (ONDNTA, C{sub 3}H{sub 6}N{sub 6}O{sub 5}) is found to be formed with complete scrambling of the N-NO bond, suggesting an N-N bond cleavage and a radical recombination process in its formation. One of the hydrogen containing products, H{sub 2}O, exhibits a DKIE of 1.5 {plus_minus} 0.1. In contrast, CH{sub 2}O and ONDNTA have DKIEs of 1.05 {plus_minus} 0.1 and 1.05 {plus_minus} 0.2, respectively, indicating that hydrogen transfer is not involved in the rate-limiting step of the reaction pathway leading to the formation of these products. 21 refs., 6 figs., 7 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 458808
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 22 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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