The potential energy profile of the decomposition of 1,1-diamino-2,2-dinitroethylene (FOX-7) in the gas phase

Abstract

1,1-Diamino-2,2-dinitroethene (FOX-7) is an energetic material with low sensitivity and high detonation performance, thus it has been considered as a potential replacement for traditional nitro-based energetic materials. In a recent...

Unsupervised Reaction Pathways Search for the Oxidation of Hypergolic Ionic Liquids: 1-Ethyl-3-methylimidazolium Cyanoborohydride (EMIM+/CBH–) as a Case Study

“…This method has seen great successes in validating reaction mechanisms, e.g., the Walden inversion in the S N 2 reaction 22,23 and the nitro-to-nitrite shift before forming NO. 24,25 In other words, the reaction pathways found with quantum chemistry calculations confirm the mechanisms that one hypothesizes to take place. When it comes to exploring a new reaction pathway that is out of the realm of chemical intuition, this method certainly bares its shortcomings�one could be satisfied once the intuitive pathways are identified and prematurely stop further searching.…”

“…Therefore, with both steps combined, the association between CBH – and HNO 3 should be less exothermic than predicted in the gas phase calculation. However, as has been documented in other cases, , the condensed phase environment could also lower the barrier of chemical reactions. Take the transition between v326 and v342 , a transition state where a proton is transferred from −BH 2 to −CH 2 (Figure ), as an examplethe transition state is 49.3 and 46.0 kcal/mol above v326 and v342 , respectively.…”

“…Traditionally, the reaction pathways have largely been identified following chemical intuitionby analyzing the structures of the separated reactants, one makes guesses of the structures of the intermediates (e.g., via addition or insertion mechanism) and proposes possible isomerizations that lead those intermediates to products reported by experiment. This method has seen great successes in validating reaction mechanisms, e.g., the Walden inversion in the S N 2 reaction , and the nitro-to-nitrite shift before forming NO. , In other words, the reaction pathways found with quantum chemistry calculations confirm the mechanisms that one hypothesizes to take place. When it comes to exploring a new reaction pathway that is out of the realm of chemical intuition, this method certainly bares its shortcomingsone could be satisfied once the intuitive pathways are identified and prematurely stop further searching.…”

Electron-Induced Decomposition of Solid 1,1-Diamino-2,2-dinitroethylene (FOX-7) at Cryogenic Temperatures

“…20,25 A second pathway without prior hydrogen atom shift shows the remaining nitro group can separate (169 kJ mol −1 ) forming NO 2 and leaving (NH 2 ) 2 CCO (Reaction 9), which can eliminate CO through a transition state of 62 kJ mol −1 (Reaction 10). 25 The diaminocarbene [C(NH 2 ) 2 ] fragment can further decompose to hydrogen isocyanide (HNC) and NH 2 (Reaction 11), which can combine once again with hydrogen to form ammonia according to Reaction 6. Other variations of these pathways, such as an earlier loss of an amino (NH 2 ) or nitro (NO 2 ) group, have been presented with appropriate energetics, 25 but in each case, the critical step toward carbon monoxide generation is nitro-to-nitrite isomerization in order to create a carbon−oxygen bond and detachment of this CO moiety from the remaining FOX-7 fragment during decomposition.…”

“…20 A hydrogen shift to H 2 N(NH)-CC(O)NOOH can be followed by the elimination of nitrous acid (HONO); the H 2 N(NH)CCO fragment can further decompose to hydrogen isocyanide (HNC), the amino radical (NH 2 ), and carbon monoxide (CO). Computations have focused on the weak C−NO 2 bond as a starting point to decomposition 21 and found dissociation energies of 280, 22 290, 19 293, 23 297, 24 300, 25 and 301 kJ mol −1 ; 26 these energies contrast the strong C−NH 2 bond 18 of 461, 25 467, 23 and 503 kJ mol −1 . 22 A temperature dependence of these reactions was found such that the C− NO 2 bond cleavage should be the predominate pathway above 250 K, while nitro-to-nitrite isomerization is only possible up to 500 K. 27 Molecular dynamics simulations at 3000 K suggest that the initial C−NO 2 bond cleavage occurs within 10 ps producing nitrogen dioxide (NO 2 ) and eventually molecular nitrogen (N 2 ) and water (H 2 O).…”