Tandem deprotonation/azide–tetrazole tautomerization of 4,6-diazido-N-nitro-1,3,5-triazin-2-amine in dimethylsulfoxide solutions: a theoretical study

Abstract

4,6-Diazido-N-nitro-1,3,5-triazin-2-amine (2) is a new promising high-energy organic compound that isomerizes in dimethylsulfoxide (DMSO) solutions to form unknown products with interesting 13C and 15N NMR spectroscopic characteristics. To identify these products, the relative energies and the 13C and 15N chemical shifts were calculated for various prototropic and valence isomers of 2. It was found that this diazide in DMSO solutions exists in equilibrium with the deprotonated form of 5-azido-N-nitrotetrazolo[1,5-a][1,3,5]triazin-7-amine (8). The anion 8 is also observed in DMSO solutions of energetic salts derived from 2 and guanidines or 4H-1,2,4-triazol-4-amines. The tandem transformations of 2 in DMSO solutions found may be of interest from both theoretical and practical points of view, for instance, in the synthesis of new energetic materials, using the reactions of anion 8 with various electrophilic agents.

13C and 15N NMR spectra of high‐energy polyazidocyanopyridines

“…These sets can be differentiated by the signal intensity that increases in the order N α < N γ < N β . It has been shown that the GIAO‐TPSSh/M06‐2X calculations allow one to correctly assign the signals in each of the three sets even when the differences in the chemical shifts of the signals are smaller than the overall MAD between the experimental and calculated δ N values. The correct assignment is possible owing to the fact that the calculation errors of δ N values for a given type of the azido group atoms (N α , N β or N γ ) are mostly systematic; in the case of (hetero)aromatic azides, the systematic error varies with the nature of the (hetero)aromatic core.…”

“…These sets can be differentiated by the signal intensity that increases in the order N α < N γ < N β . [31] It has been shown [6,7] that the GIAO-TPSSh/M06-2X calculations allow one to correctly assign the signals in each of…”

“…The 13 C and 15 N chemical shifts were calculated by the gauge‐independent atomic orbital (GIAO) method with the Tao–Perdew–Staroverov–Scuseria hybrid (TPSSh) functional . This approach has been successfully used to predict the 13 C and 15 N chemical shifts of many heteroaromatic azides in CDCl 3 and DMSO‐ d 6 …”

“…Meanwhile, 15 N NMR spectra provide very important information about the structure and reactivity of azido groups. [6][7][8][9][10][11][12][13] In the present work, we report on the 13 C and 15 N NMR spectra of high-energy 2,4,6-triazidopyridine-3,5dicarbonitrile (1), 2,3,5,6-tetraazidopyridine-4-carbonitrile (2) and 3,4,5,6-tetraazidopyridine-2-carbonitrile (3) in CDCl 3 . The most probable single-bond rotamers of polyazides 1-3 are represented in Scheme 1.…”

“…[20] This approach has been successfully used to predict the 13 C and 15 N chemical shifts of many heteroaromatic azides in CDCl 3 and DMSO-d 6 . [6,7] Experimental Synthesis Compounds 1-3 were prepared by azidation of the corresponding chlorides with sodium azide in acetone, according to the procedures described in the literature. [21] NMR measurements 13 C and 15 N NMR spectra were recorded at 294 K for~0.4 M solutions in CDCl 3 on a Bruker Avance III 500 spectrometer, equipped with a 5-mm Broadband Observe (BBO) probehead operating at 125 MHz for 13 C and 50 MHz for 15 N. The 1 H-decoupled 13 C NMR spectra were obtained by averaging 100-200 signal accumulations.…”