Thermal decomposition of energetic materials. 45. Fast thermolysis patterns of energetic oxamides

Fast thermal decomposition (dT/dt=70-80°C sec^–1) of four energetic oxamides [N,N-bis(2-nitratoethyl) oxamide, N,N-bis(3-nitratopropyl)oxamide, N,N-bis(2-nitratopropyl)oxamide, and N,N-bis(2-azidoethyl)oxamide] in Ar is described by FTIR/temperature profiling. The product sequence and temperatures are used to analyze how the alkyl chain length, the position of the nitrate ester group, and the nature of the energetic group affect the thermolysis process. The crystal structure of N,N-bis(3-nitratopropyl)oxamide was determined: monoclinic,P2₁/c,a=5.125(2),b=6.906(2),c=18.441(8) Å,=94.91(3)°,V=650.3(4) ų,Z=2,D=1.502 g cm^–3,R(F)=0.036,R(wF)=0.044.     

Comparison of Young's modulus and specific heat anomalies at the magnetic transition in α′-NaV2O5

We have measured Young's modulus (using a vibrating reed technique) and the specific heat (using ac calorimetry) on the same crystals of α′-NaV₂O₅ at its T_c=34 K magnetic phase transition. Both properties exhibit large, unsymmetrical, and sample-dependent anomalies. While the specific heat results suggest tricritical behavior of the transition, large fluctuation effects are observed in the modulus above T_c. Fits of the modulus in terms of the specific heat, entropy, and free energy suggest that fluctuations are strongly stress- and sample-dependent.     

Ueber das Polvierseit

Ohne Zusammenfassung     

Ueber die algebraischen Functionen und ihre Anwendung in der Geometrie

Ohne ZusammenfassungDer vorliegende Aufsatz ist die Ausführung einer in den Göttinger Nachrichten (Febr. 1873) enthaltenen Note der Verfasser. — Ein Auszug aus dem Folgenden ist von Herrn Fiedler in die soeben erschienene Uebersetzung der 2. Ausgabe des Salmon'schen Werkes über höhere ebene Curven aufgenommen worden.     

Ueber diejenigen Curven eines Büschels,welche eine gegebene Curve zweipunktig berühren

Ohne Zusammenfassung     

Total Synthesis of (+)-6-epi-Ophiobolin A

The ophiobolin sesterterpenes are notable plant pathogens which have recently elicited significant chemical and biological attention because of their intriguing carbogenic frameworks, reactive functionalities, and emerging anticancer profiles. Reported herein is a total synthesis of (+)-6-epi-ophiobolin A in 14 steps, a task which addresses construction of the synthetically challenging spirocyclic tetrahydrofuran motif as well as several other key stereochemical problems. This work demonstrates a streamlined synthetic platform to complex ophiobolins leveraging disparate termination modes of a radical polycyclization cascade for divergent elaboration and functionalization.     

Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave-induced plasma detector

Fluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave-induced plasma detector (GC-MIPD), which permits fluorine-selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium-sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC-MIPD system were determined to be 4.8 pg-F/s, 1060, and 5000, respectively. The utility of this GC-MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.