Decades after the initial discovery of bis (2,4,6trinitrophenyl) ether derivatives, the first single-crystal X-ray structures for three members of this compound class can finally be shown and the analytical data could be completed. This group of molecules is an interesting example that illustrates why older predictive models for the sensitivity values of energetic materials like bond dissociation enthalpy and electrostatic potential sometimes give results that deviate significantly from the experimentally determined values. By applying newer models like Hirshfeld surface analysis and fingerprint plot analysis that utilize the crystal structure of an energetic material, the experimentally found trend of sensitivities could be understood and the older models could be brought into a proper perspective. In the future, the prediction of structure−property relationships for energetic molecules starting from a crystal structure can be achieved and should be pursued.

Recently the investigation of the correlation between the crystal structure and important properties such as the sensitivity and thermostability of energetic materials has gained more and more interest among experts in the field. To contribute to this development, several models for the sensitivity prediction of energetic materials have been applied to the title compounds. Very often, older models that focus on bond dissociation enthalpy or electrostatic potential result in values that differ significantly from values of actual measurements. However, more recent models such as Hirshfeld surface analysis and fingerprint plot analysis offer an improved correlation between prediction and practical tests. We compared these methods with the aforementioned older models and gained further insight into the structure−property relationships of energetic materials. The accuracy of predictions of structure− property relationships that can be deduced from a crystal structure increases with the sample size over time. Therefore, this method should be pursued and applied to different energetic materials in the future, for a better understanding of those relationships.

Two improved, fast, feasible, scalable, and economic synthetic protocols for the laboratory scale manufacturing of 3,5-dinitro-1-(2,4,6-trinitrophenyl)-1H-pyrazol-4-amine (PicADNP) are described. The previous set of analytical data from an earlier publication could be verified and complemented by additional measurements. The material was fully characterized by multinuclear NMR, spectroscopic methods, elemental analysis, DSC and DTA, as well as X-ray diffraction. The crystal structure was elucidated and Hirshfeld surface analysis, as well as 2D fingerprint plot analysis for the assessment of sensitivities towards external stimuli was applied. The sensitivity towards shock, friction and electrostatic discharge was also determined exper-imentally. The performance of the title compound was calculated by applying the EXPLO5 computer code and the theoretical results were compared with the results of SSRT and booster testing experiments. The title compound combines good energetic properties with improved safety characteristics and could find its way into application as a new booster explosive to replace the state-of-the-art material PETN. The optimizations of the synthetic protocol comprise a greener solvent system, shorter reaction times, higher yields for the pure material and a nontoxic byproduct to make the manufacturing process more attractive and better suitable for a subsequent scale up to the technical and industrial scale.

An optimized synthetic procedure for the manufacture of picryl bromide on a 300 g scale is described. Previous procedures had different drawbacks such as two or more separate nitration steps with varying mixed acids, a complicated workup and purification procedure, expensive starting materials, or very long reaction times. An optimized and time-efficient method on a laboratory scale was described in an earlier conference contribution. The one-pot nitration of bromobenzene using a 5:1 mixed acid consisting of oleum (30%) and white-fuming nitric acid (10 equiv) was developed to prove the technical scalability of the reaction. By application of the optimized reaction parameters to a large-scale environment, crude picryl bromide yields of up to 72% can be achieved. The product contains only a minor picric acid impurity (2−3%), which is formed during the aqueous workup step. It can be removed by a single recrystallization from boiling chloroform to afford the target compound in pure form. This method combines the use of cheap materials with a time-efficient route of synthesis and a simple purification step, which is an improvement compared with the stateof-the-art methods.

Previous reports showed, that tris(2,2,2trinitroethoxy)methane, also known as tris(2,2,2-trinitroethyl) orthoformate or trinitroethyl formate (TNEF), exhibits a very high potential for application due to its excellent energetic properties and compatibility with state of the art binder systems for composite propellants. However, TNEF was never produced on a scale exceeding a few grams. In this work, a scaled and optimized synthetic procedure for the manufacturing of elemental analysis pure TNEF in a 100 g pre-technical scale is described. Applied optimizations focus on cost of the synthesis and improvements regarding a greener purification process. Acceptable yields were achieved in the 100 g scale and the described synthetic procedure could be easily applied in the technical scale in the next step. This could stimulate a broader application of TNEF as an environmentally benign high energy density oxidizer for composite propellants.