Engineering topics
Publications and source records attributed to Leonard, Philip W..
We report a [3+2] cycloaddition using 3,6-bis-propargyloxy-1,2,4,5-tetrazine and azides to synthesize energetic polymers containing 1,2,4,5-tetrazine within the scaffold.
Three new low melting compositions have been developed here based on the ingredients amino-1,2,4-triazolium nitrate, 3,5-diamino-1,2,4-triazolium nitrate and ammonium nitrate, to create the formulation AAD, in addition to mixtures comprising guanidinium 5-amino-tetrazolate and ammonium nitrate in either a 1 : 3 or 1 : 6 mole ratio (GAN13 and GAN16 respectively). The materials melt in the range of 95–100 °C and do not begin to decompose until >195 °C. The formulations are insensitive to impact, spark and friction and were calculated to show promising explosive performance properties (V D =8.78–9.0 km/s, P CJ =28.4–30.6 GPa). HMX mixtures of AAD, GAN13 and GAN16 were also prepared and these materials were characterized with respect to their safety and performance as well.
The reaction of 3,4–dinitropyrazole, 5–nitrotetrazole, or 4–nitro–1,2,3–triazole with 1,2,4,5–tetrazines substituted with 3,5–dimethylpyrazolyl (dmp) groups results in energetic cocrystals after 1 minute of reflux and cooling to room temperature in yields of 89–92 %. Hydrogen–bonding between the dmp group to the N–H of the energetic heterocycles are the predominant interaction that stabilizes the new cocrystals. Each cocrystal packs in a different lattice structure and the cocrystals with sheet–like and herring–bone crystal packing orientations are less sensitive than the cocrystal with the interlocked structure. Electrostatic potential mapping helps rationalize why dmp–substituted tetrazines readily form cocrystals, whereas more electron–deficient pyrazolyl tetrazines do not. Furthermore, the calculated energetic performance of the new cocrystals approaches that of 2,4,6–trinitrotoluene (TNT) and importantly, these materials will aid in the rational design of new cocrystalline energetic materials.
In the molecule of neutral bis[(1H-tetrazol-5-yl)methyl]nitramide, (I), C 4 H 6 N 10 O 2 , there are two intramolecular N—H∙∙∙O hydrogen bonds. In the crystal, N—H∙∙∙N hydrogen bonds link molecules, forming a two-dimensional network parallel to (-201) and weak C—H∙∙∙O, C—H∙∙∙N hydrogen bonds, and intermolecular π–π stacking completes the three-dimensional network. The anion in the molecular salt, triaminoguanidinium 5-({[(1H-tetrazol-5-yl)methyl](nitro)amino}methyl)tetrazol-1-ide, (II), CH 9 N 6 + ·C 4 H 5 N 10 O 2 - , displays intramolecular π–π stacking and in the crystal, N—H∙∙∙N and N—H∙∙∙O hydrogen bonds link the components of the structure, forming a three-dimensional network. In the crystal of diammonium bis[(tetrazol-1-id-5-yl)methyl]nitramide monohydrate, (III), 2NH 4 + ·C 4 H 4 N 10 O 2 2- ·H 2 O, O—H∙∙∙N, N—H∙∙∙N, and N—H∙∙∙O hydrogen bonds link the components of the structure into a three-dimensional network. In addition, there is intermolecular π–π stacking. In all three structures, the central N atom of the nitramide is mainly sp 2 -hybridized. Bond lengths indicate delocalization of charges on the tetrazole rings for all three compounds. Compound (II) was found to be a non-merohedral twin and was solved and refined in the major component.
We report that in the title compound, C 5 HN 7 , the nitrile and azido substituents are close to being coplanar with the central ring. Molecules in the crystal are linked via an N—H...N hydrogen bond to a nitrile acceptor, forming a chain extending along the c- axis direction.
In the title compound, C 5 N 6 , all the atoms are approximately coplanar. In the crystal, molecules are packed with short contact distances of 2.885 (2) (between the diazo N atom connected to the ring and a cyano N atom on a neighboring molecule) and 3.012 (2) Å (between the terminal diazo N atom and an N atom of a neighboring imidazole ring).
Here, the title compound, C 3 H 2 N 4 O 4 , forms crystals with two molecules in the asymmetric unit which are conformationally similar. With the exception of the O atoms of the nitro groups, the molecules are essentially planar. In the crystal, adjacent molecules are associated by N—H...N hydrogen bonds involving the imidazole N—H donors and N-atom acceptors of the unsaturated nitrogen of neighboring rings, forming layers parallel to (010).