Thermal decomposition of RDX from reactive molecular dynamics

We use the recently developed reactive force field ReaxFF with molecular dynamics to study thermal induced chemistry in RDX [cyclic-[CH(2)N(NO(2))](3)] at various temperatures and densities. We find that the time evolution of the potential energy can be described reasonably well with a single exponential function from which we obtain an overall characteristic time of decomposition that increases with decreasing density and shows an Arrhenius temperature dependence. These characteristic timescales are in reasonable quantitative agreement with experimental measurements in a similar energetic material, HMX [cyclic-[CH(2)N(NO(2))](4)]. Our simulations show that the equilibrium population of CO and CO(2) (as well as their time evolution) depend strongly of density: at low density almost all carbon atoms form CO molecules; as the density increases larger aggregates of carbon appear leading to a C deficient gas phase and the appearance of CO(2) molecules. The equilibrium populations of N(2) and H(2)O are more insensitive with respect to density and form in the early stages of the decomposition process with similar timescales.     

Spektroskopische Bestimmung der Doppelbindungslage in Phospholinen

Zusammenfassung Die Spin-Spin-Kopplungskonstanten der olefinischen Protonen mit dem ³¹P sowie die Feinstruktur der ¹H-NMR-Spektren sind charakteristisch für die Lage der Doppelbindung. Vielfach kann auch die Intensität der _C=C-Schwingung im IR zur Bestimmung der Doppelbindungslage benutzt werden. Massenspektren geben nur in Ausnahmefällen Hinweise, können jedoch zur exakten Bestimmung des Molekulargewichts dienen.

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Summary The spin-spin coupling constants of the olefinic protons with the phosphorus-31 as well as the fine structure of the nmr-spectra are characteristic for the position of the double bond. In the infrared, the intensity of the _C=C-frequency may often serve as indication of the position of the double bond. The applicability of mass spectra is limited to a small number of compounds. They may be used, however, for an accurate determination of the molecular weight.

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Die Ausführung der Untersuchungen erfolgte unter Mitarbeit von Herrn F. Dlugosch, Herrn H. Au und Fräulein R. Barth.

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Herrn Dr. C. A. Reilly, Shell-Development Company, Emeryville, USA, danken wir für die Überlassung getesteter Programmkartensätze zur Berechnung der NMR-Spektren.     

Alkoholyse von Tris(dimethylamino)-arsin

Alcoholysis of Tris (dimethylamino)arsine The reaction of tris(dimethylamino)arsine with alcoholes and thioles leads to the formation of esters of the general formula As(XR)₃ (X = O and S). The reaction is a suitable preparative method for the synthesis of the esters As(XR)₃ (X = O and S). By alcoholysis in steps results an equilibrium system containing the molecules AsX₃, AsX₂Y, AsXY₂, and AsY₃ (X = OR, Y = N(CH₃)₂).     

3-Dimethylarsino-propylamin, (CH3)2As?(CH2)3?NH2, und Bis-[3-amino-propyl]-methylarsan,CH3As[(CH2)3?NH2]2

3-Dimethylarsino-propylamine, (CH₃)₂As? (CH₂)₃? NH₂, and Bis-[3-aminopropyl]-methylarsane, CH₃As[(CH₂)₃? NH₂]₂ The reduction of the nitriles Me₂As(CH₂)₂? CN (Me?CH₃) and MeAs(CH₂CH₂? CN)₂ results in the formation of the arsines Me₂As(CH₂)₃? NH₂ and MeAs[(CH₂)₃? NH₂]₂, respectively. The reactivity of these compounds, especially the formation of carbonyl complexes and heterocyclic compounds are described.     

Application of the energy gap law to the decay of charge transfer excited states,solvent effects

Values of non-radiative decay rate constants (k_nr) and emission energies (E_cm) have been obtained for Os(Phen₃)²⁺ in a series of solvents and the results are consistent with the energy gap law. For hydroxylic solvents like water or methanol related studies suggest the existence of strong, specific contributions to the vibrational trapping energy of the solvent.     

Alkyl-Diol Silica (ADS): restricted access precolumn packings for direct injection and coupled-column chromatography of biofluids

The direct and repetitive injection of untreated biological fluids (e.g., hemolyzed blood, plasma, serum, cell culture and tissue homogenates) onto an HPLC-system and the subsequent analysis of low-molecular weight compounds (e.g. drugs, xenobiotics, metabolites) is rendered possible by a coupled-column configuration and special precolumn packings. For this purpose a new family of chemically and enzymatically tailored reversed-phase packing materials have been prepared. The LC-integrated sample clean-up with these restricted access (bimodal) phases is based on the complete nonadsorptive size exclusion of macromolecules (e.g. proteins) and on the simultaneous dynamic partitioning of the target molecules. The bonded phase which exclusively covers the internal pore surface of a glyceryl-modified silica is a butyryl-(C-4), capryloyl-(C-8) or stearoyl-(C-18) moiety. These ligands allow a classical reversed-phase or ion-pair chromatography during the sample work-up step. The capacity of the n-alkyl phase is comparable with conventional silica based RP-materials. The broad hydrophobic retentive capability of these packings allows the extraction of a wide variety of compounds of biomedical interest. The electroneutral and hydrophilic particle exterior (glyceryl-residues) was generated using either soluble or immobilized enzymes (lipase, esterase) which cleave the fatty acid esters exclusively at the outer surface. Unwanted macromolecular components of a sample (e.g. proteins) are quantitatively eluted in the void volume due to the restricted access given by the pore size (6 nm) and the nonadsorptive external diol coverage. The lifetime of a precolumn (25 × 4 mm I.D.) packed with these novel bimodal, i.e. RP-SEC phases exceeds more than 200 injections of 500 l plasma. In addition to the synthesis, this paper describes an application of each of these Alkyl-Diol Silica (ADS) precolumn packings in fully automated coupled-column HPLC systems for the analysis of drugs and endogenous compounds in different biological matrices.Dedicated to Professor Dr. Dr. h.c. mult. J.F.K. Huber on the occasion of his 70th birthday     

Cyclic esters of aliphatic diacids with pyrocatechol and hydroquinone

Cyclic esters of adipic acid, suberic acid and sebacic acid were prepared by reaction of the acid dichlorides and pyrocatechol or hydroquinone in benzene under high dilution conditions. While only the cyclic dimers could be obtained from hydroquinone, pyrocatechol formed cyclic monomers as well as cyclic dimers (and also a cyclic dimer with succinic acid). The structure of all compounds was confirmed by¹H-NMR- and mass spectra. The crystal structures of the pyrocatechol esters were determined by single crystal X-ray analysis.

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Cyclische Ester aliphatischer Dicarbonsäuren mit Brenzcatechin und Hydrochinon

Zusammenfassung Es wurden cyclische Ester von Adipinsäure, Korksäure und Sebacinsäure durch Reaktion der entsprechenden Säure-Dichloride mit Brenzcatechin oder Hydrochinon bei hoher Verdünnung hergestellt. Während mit Hydrochinon lediglich die cyclischen Dimeren erhalten werden konnten, wurden mit Brenzcatechin sowohl cyclische Monomere als auch cyclische Dimere erhalten (ebenfalls das cyclische Dimer mit Bernsteinsäure). Die Strukturen wurden mittels¹H-NMR und Massenspektren gesichert. Die Kristallstrukturen der Brenzcatechin-Ester wurden mittels Röntgenstrukturanalyse bestimmt.