Stereochemically pure phosphines with phosphorus‐heteroatom bonds and P‐centered chirality are a promising class of functional building blocks for the design of chiral ligands and organocatalysts. A route to enantiomerically pure primary aminophosphine sulfides was opened through stereospecific reductive C−N bond cleavage of phosphorus(V) precursors by lithium in liquid ammonia. The chemoselectivity of the reaction as a function of reaction time, substrate pattern, and chiral auxiliary was investigated. In the presence of exclusively aliphatic groups bound to the phosphorus atom, all competing reductive side reactions are totally prevented. The absolute configurations of all P‐stereogenic compounds were determined by single‐crystal X‐ray diffraction analysis. Their use as synthetic building blocks was demonstrated. The lithium salt of (R)‐BINOL‐dithiophosphoric acid proved to be a useful stereochemical probe to determine the enantiomeric purity. Insights into the coordination mode of the lithium‐based chiral complex formed in solution was provided by NMR spectroscopy and DFT calculations.
The Global Threat Reduction Initiative Program continues to develop existing and new test reactor fuels to achieve the maximum attainable uranium loadings to support the conversion of a number of the world's remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Currently, the program is focused on assisting with the development and qualification of a fuel design that consists of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix. Thermal conductivity is an important consideration in determining the operational temperature of the fuel and can be influenced by interaction layer formation between the dispersed phase and matrix, porosity that forms during fabrication of the fuel plates or rods, and upon the concentration of the dispersed phase within the matrix. This paper develops and validates a simple model to study the influence of interaction layer formation, dispersed particle size, and volume fraction of dispersed phase in the matrix on the effective conductivity of the composite. The model shows excellent agreement with results previously presented in the literature. In particular, the thermal conductivity of the interaction layer does not appear to be as important in determining the effective conductivity of the composite, while formation of the interaction layer and subsequent consumption of the matrix reveals a rather significant effect. The effective thermal conductivity of the composite can be influenced by the dispersed particle distribution by minimizing interaction layer formation and preserving the higher thermal conductivity matrix.
The synthesis of the polynitroaromatic compound pentanitrobenzene was re-examined by modern spectroscopic, structural and physicochemical methods. Originally prepared in 1979, this material could exhibit interesting properties as an oxygen-rich energetic building block. The energies of formation were calculated with the GAUSSIAN program package and the detonation parameters were pre-* Prof. Dr. T. M. Klapötke 126 dicted using the EXPLO5 computer code. The performance data were determined and compared to the common oxidizer ammonium perchlorate. The crystal structure of pentanitrobenzene was determined by Xray crystallography, and those of 2,3,4,6-tetranitroaniline and styphnic acid (trinitroresorcinol) were re-determined. in 1979; [7] characterization was achieved by 1 H NMR, mass spectrum and elemental analysis. A little later in 1990, the 13 C and 14 N NMR spectroscopic data followed without assignments. [8] Since then, no further reports with new information regarding pentanitrobenzene appeared. In this contribution we would like to re-investigate and study the properties of pentanitrobenzene.
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