Thermal unimolecular decomposition mechanism of 2,4,6-trinitrotoluene: a first-principles DFT study |
| |
Authors: | Xiao-Fang Chen Ji-Feng Liu Zi-Hui Meng Ke-Li Han |
| |
Institution: | (1) State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian, People’s Republic of China;(2) Department of Chemical and Environmental Engineering, Beijing Institute of Technology, 100081 Beijing, People’s Republic of China; |
| |
Abstract: | Simple C–NO2 homolysis, 4,6-dinitroanthranil (DNAt) production by dehydration, and the nitro-nitrite rearrangement–homolysis for gas-phase
TNT decomposition were recently studied by Cohen et al. (J Phys Chem A 111:11074, 2007), based on DFT calculations. Apart from those three pathways, other possible initiation processes were suggested in this
study, i.e., CH3 removal, O elimination, H escape, OH removal, HONO elimination, and nitro oxidizing adjacent backbone carbon atom. The intermediate,
3,5-dinitro-2(or 4)-methyl phenoxy, is more favor to decompose into CO and 3,5-dinitro-2(or 4)-methyl-cyclopentadienyl than
to loss NO following nitro-nitrite rearrangement. Below ~1,335 K, TNT condensing to DNAt by dehydration is kinetically the
most favor process, and the formations of substituted phenoxy and following cyclopentadienyl include minor contribution. Above
~1,335 K, simple C–NO2 homolysis kinetically dominates TNT decomposition; while the secondary process changes from DNAt production to CH3 removal above ~2,112 K; DNAt condensed from TNT by dehydration yields to that by sequential losses of OH and H above ~1,481 K
and to nitro-nitrite rearrangement–fragmentation above ~1,778 K; O elimination replaces DNAt production above ~2,491 K, playing
the third role in TNT decomposition; H escaping directly from TNT thrives in higher temperature (above ~2,812 K), as the fourth
largest process. The kinetic analysis indicates that CH3 removal, O elimination, and H escape paths are accessible at the suggested TNT detonation time (~100–200 fs), besides C–NO2 homolysis. HONO elimination and nitro oxidizing adjacent backbone carbon atom paths are negligible at all temperatures. The
calculations also demonstrated that some important species observed by Rogers and Dacons et al. are thermodynamically the
most favor products at all temperatures, possibly stemmed from the intermediates including 4,6-dinitro-2-nitroso-benzyl alcohol,
3,5-dinitroanline, 2,6-dinitroso-4-nitro-phenylaldehyde, 3,5-dinitro-1-nitrosobenzene, 3,5-dinitroso-1-nitrobenzene, and nitrobenzene.
All transition states, intermediates, and products have been indentified, the structures, vibrational frequencies, and energies
of them were verified at the uB3LYP/6-311++G(d,p) level. Our calculated energies have mean unsigned errors in barrier heights
of 3.4–4.2 kcal/mol (Lynch and Truhlar in J Phys Chem A 105:2936, 2001), and frequencies have the recommended scaling factors for the B3-LYP/6-311+G(d,p) method (Andersson and Uvdal in J Phys
Chem A 109:2937, 2005; Merrick et al. in J Phys Chem A 111:11683, 2007). All calculations corroborate highly with the previous experimental and theoretical results, clarifying some pertinent questions. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|