The introduction of a monofluoromethyl moiety has undoubtedly become a very important area of research in recent years. Owing to the beneficial properties of organofluorine compounds, such as their metabolic stability, the incorporation of the CH2F group as a bioisosteric substitute for various functional groups is an attractive strategy for the discovery of new pharmaceuticals. Furthermore, the monofluoromethyl unit is also widely used in agrochemistry, in pharmaceutical chemistry, and in fine chemicals. The problems associated with climate change and the growing need for environmentally friendly industrial processes mean that alternatives to the frequently used CFC and HFBC fluoromethylating agents (CH2FCl and CH2FBr) are urgently needed and also required by the Montreal Protocol. This has recently prompted many researchers to develop alternative fluoromethylation agents. This Minireview summarizes both the classical and new generation of fluoromethylating agents. Reagents that act via electrophilic, nucleophilic, and radical pathways are discussed, in addition to their precursors.
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.
The large-scale production
of solid-state batteries necessitates
the development of alternative routes for processing air-sensitive
thiophosphate-based solid electrolytes. To set a basis for this, we
investigate the chemical stability and ionic conductivity of the LGPS-type
lithium-ion conductor tetra-Li7SiPS8 (LiSiPS)
processed with various organic solvents. We elucidate the nature of
colorful polysulfides that arise during solvent treatment and trace
back their origin to the dissolution of the Li3PS4-type amorphous side phase typically present in LiSiPS. We find that
water and alcohols decompose LiSiPS by the nucleophilic attack into
oxygen-substituted thiophosphates and thioethers and propose a reaction
mechanism for the latter. Moreover, we confirm that quaternary thiophosphates
can be recrystallized from MeOH solutions upon subsequent high-temperature
treatment. Aprotic solvents with donor numbers smaller than 15 kcal
mol–1 are suitable for wet-processing quaternary
thiophosphates because both the crystal structure of the electrolyte
and a high ionic conductivity of >1 mS cm–1 are
retained. Using anisole as a case study, we clarify that a residual
water content of up to 800 ppm does not lead to a significant deterioration
in the ionic conductivity when compared to dry solvents (≤5
ppm). Additionally, we observe a decrease in ionic conductivity with
an increasing amount of the solvent residue, which depends not only
on the donor number of the solvent but also on the vapor pressure
and interactions between the solvent molecules and thiophosphate groups
in the solid electrolyte. Thus, optimization of solvent-processing
methods of thiophosphate electrolytes is a multifaceted challenge.
This work provides transferable insights regarding the stability of
LiSiPS against organic solvents that may enable competitive and large-scale
thiophosphate-based solid electrolyte processing.
Fluoromethyl)triphenylphosphonium iodide has been prepared in a simple and high yield synthesis. The salt was characterized by vibrational, NMR spectroscopy and a single-crystal X-ray structure analysis. The salt crystallizes in an orthorhombic space group Pna2 1 with four formula units in the
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.
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