Theoreticalab InitioStudy of CN₂O₂Structures:  Prediction of Nitryl Cyanide as a High-Energy Molecule

Abstract

Structures, energies, and harmonic vibrational frequencies of CN2O2 isomers have been investigated theoretically at the ab initio CCSD(T)/TZ2P//MBPT(2)/6-31G* level in search of new high-energy molecules and in a study of the mechanism of the reaction between NCO and NO radicals. Nitrosoisocyanate, ONNCO (1), earlier studied as a collision complex in the reaction of NCO and NO (Lin, M. C.; Melius, C. F. J. Phys. Chem. 1993 , 97, 9124) is the most energetically favorable CN2O2 isomer, but its 18 kcal/mol unimolecular dissociation barrier is very low. Thus 1 can only be observed as a short-lived intermediate. However, nitrosofulminate, ONCNO (8), and nitryl cyanide, NCNO2 (12), higher energy isomers (69 and 38 kcal/mol above trans- 1a, respectively), are more stable than 1 toward decomposition. This offers species 8 and 12 as interesting molecules for experimental study. Moreover, 12 can be a reasonably stable molecule as its C−N bond dissociation energy (59 kcal/mol) and the barrier to decomposition into N2 and CO2 (54 kcal/mol) are rather high, being comparable to those of nitromethane. The estimated large values of the heat of formation (ΔH f°300 = 60 kcal/mol) and of the decomposition energy of 12 (12 → N2 + CO2; ΔE = 150 kcal/mol) make this species potentially interesting as a high-energy molecule. Our study also includes four- (2) and three-membered (17) cyclic and bicyclic (3) isomers. The C s cyclic isomers, 2 and 17, are extremely unstable, but the bicyclic C 2 v form (3) has a 29 kcal/mol dissociation barrier and should be observable.

Quantum chemical, ballistic and explosivity calculations on 2,4,6,8-tetranitro-1,3,5,7-tetraaza cyclooctatetraene: A new high energy molecule

“…2,4,6,8-tetranitro-1,3,5,7-tetraazacycloocta tetraene possesses several features that make it interesting. The molecular set (1)(2)(3)(4) of interest in the present study is:…”

“…Based on the heat of formation and mass density, the trimer (NO 2 CN) 3 , analogue of RDX has been predicted [1,2] to be a high energy molecule. It should be noted that the tetramer of (NO 2 CN) n , the HMX analogue, however, has not been studied in this respect.…”

Bicyclic CN2O2 as a high-energy density material: promising or not?

“…To help lower the synthetic cost, a reliable computational prediction on the intrinsic stability of a HEDM would be highly 11 Among the various structures they obtained, they found that a branched isomer B (nitryl cyanide) and a bicyclic isomer C (see Scheme 1) both contain large exothermicity (150 and 190 kcal mol À1 , respectively) and high decomposition barrier (54 and 29 kcal mol À1 , respectively) to N 2 + CO 2 at the CCSD(T)/TZ2P//MP2/6-31G(d) level. One is to computationally nd a candidate with both high energy and high barrier towards decomposition.…”

Theoretical studies on the formation mechanism and explosive performance of nitro‐substituted 1,3,5‐triazines

“…3 Before estimating the explosive property of TNTA, they also suggested nitryl cyanide, NO 2 CN (4), as a high-energy molecule among the isomers of CN 2 O 2 . 4 Like many other derivatives of 1,3,5-triazine (s-triazine, 5), one can imagine that TNTA could possibly be made by direct cyclic trimerization of nitryl cyanide. An applicable method involves trimerization of suitable cyanides, 3RCN ?…”

“…9 It is well known that melamine can be made by heating cyanamide, NH 2 CN (8), ammonium dicyanamide NH 4 [N(CN) 2 ], or dicyandiamide (cyanoguanidine) (9) as mentioned by Schnick and coworkers (Scheme 1). 10 Similarly, TNTA should be made by heating 4 if the reaction takes place through the same route.…”