Organoantimony compounds : VIII. Cleavage of Sb—O—Sb bonds in μ—oxybis(triphenyl -chloroantimony) and triphenylantimony oxide by methanol and acetylacetone

SbOSb bonds in (Ph₃ClSb)₂O and PH₃SbO are cleaved readily by methanol and acetylacetone. The reactions provide convenient synthetic routes for Ph₃Sb(OMe)Cl, Ph₃Sb(OMe)₂, Ph₃Sb(acac)Cl, and Ph₃Sb(acac)OH. Characterization of these compounds by infrared, Raman, and ¹H NMR spectral measurements is reported.     

Organobismuth compounds : V. Preparation,characterization, and properties of triphenylbismuth diazide and dicyanide

Triphenylbismuth diazide and the dicyanide have been prepared and characterized. Previously reported triphenylbismuth hydroxide cyanide has been shown to be triphenylbismuth dicyanide. A trigonal bipyramidal structure is indicated for both the compounds on the basis of their infrared and laser Raman spectra. The molecular weight and conductance data for the diazide in acetone are also in accord with a molecular structure. The dicyanide is, however, decomposed in solution into diphenylbismuth cyanide and benzonitrile. Thermal decomposition of the solid dicyanide and the diazide has also been studied. The possibility of the conversion of the diazide and the dicyanide into the corresponding dicyanate has been explored. Unlike transition metal azides, the triphenylbismuth diazide does not react with CO. Triphenylbismuth dicyanide could also not be converted into the corresponding dicyanate by reaction with either HgO or MnO₂. Reaction with HgO afforded triphenylbismuth oxide and the reaction with MnO₂ gave uncharacterized products.     

Effect of structure on the thermal stability of polyimides

Polyimides with different proportions of m-phenylene and p-phenylene (or p,p′-biphenylene) were prepared by polymerizing different molar ratios of m-phenylene diamine and p-phenylene diamine (or p,p′-diaminobiphenyl) with pyromellitic dianhydride in dimethylformamide at 0°C. Chemical cyclodehydration of polyamic acids resulted in the corresponding polyimides. Polymers were characterized by infrared (IR), viscosity, and density measurements. Viscosity and density of polymers decreased with an increase on m-phenylene groups in the backbone. The thermal and thermooxidative stabilities were investigated by dynamic thermogravimetry. Stability decreased when m-phenylene groups were introduced in the backbone.     

Superstable implicit Runge-Kutta methods for second order initial value problems

Using the well known properties of thes-stage implicit Runge-Kutta methods for first order differential equations, single step methods of arbitrary order can be obtained for the direct integration of the general second order initial value problemsy=f(x, y, y),y(x _o)=y _o,y(x _o)=y _o. These methods when applied to the test equationy+2y+ ² y=0, ,0, +>0, are superstable with the exception of a finite number of isolated values ofh. These methods can be successfully used for solving singular perturbation problems for which f/y and/or f/y are negative and large. Numerical results demonstrate the efficiency of these methods.     

Preparation of cesium trimolybdate by the thermal decomposition of a new oxomolybdenum(VI) oxalato complex

A new molybdenum(VI) complex Cs₂(NH₄)2[Mo₃O₈(C₂O₄)₃] (CAMO) has been prepared and characterized by chemical analysis and IR spectral studies. Thermal decomposition studies have been made using TG, DTA and DTG techniques. The compound is anhydrous and stable up to 160°C. Thereafter it decomposes in three stages. The first and the second stages occur in the temperature ranges 160–220°C and 220–280°C to give the intermediate compounds having the tentative compositions Cs₄(NH₄)₂[Mo₆O₁₆(C₂O₄)₃(CO₃)₂] and Cs₄[Mo₆O₁₆(C₂O₄)₂(CO₃)₂] respectively, the later then decomposing to give the end product Cs₂Mo₃O₁₀ at 370°C. The end product was characterized by chemical analysis, IR spectral and X-ray studies.     

Simultaneous determination of nitrogen and lithium by thermal neutron activation analysis

The determination of lithium and nitrogen in a variety of materials by thermal neutron activation is described. The nuclear reactions used are ¹⁴N(n,p)¹⁴C and ⁶ Li(n,α)³H. Radionuclides. ¹⁴C and ³H for counting are isolated by fusion of the irradiated sample in a vacuum system. Data are presented on lithium and nitrogen concentrations in several terrestrial standards. The new method allows reliable measurements on 10–50-mg samples.     

Highly Efficient Non‐Palladium‐Catalyzed Controlled Synthesis and X‐ray Analysis of Functionalized 1,2‐Diaryl‐, 1,2,3‐Triaryl‐, and 1,2,3,4‐Tetraarylbenzenes

A general, two‐step, highly efficient synthesis of 1,2‐diaryl‐, 1,2,3‐triaryl‐, and 1,2,3,4‐tetraarylbenzenes from simple stitching of α‐oxo‐ketene‐S,S‐acetals and active methylene compounds via a lactone intermediate is described. This procedure offers easy access to highly functionalized arylated benzenes that contain sterically demanding groups in good to excellent yields. The novelty of the procedure lies in the construction of aromatic compounds with the desired conformational flexibility along the molecular axis in a transition‐metal‐free environment through easily accessible precursors. Crystal analysis of these arylated benzene scaffolds showed that the peripheral aryl rings are arranged in a propeller‐like fashion with respect to the central benzene ring. Examination of the crystal packing in the structure of a 1,2,3,4‐tetraarylbenzene revealed an N???π interaction between molecules related by a two‐fold screw axis running in the direction of the a axis. Interestingly, the repeating array of N???π interactions around the axis of this 1,2,3,4‐tetraarylbenzene forces the molecules into a helical pattern.     

Chiral separation of labetalol stereoisomers in human plasma by capillary electrophoresis

A newly derivatized cyclodextrin [octakis-(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin] was investigated as a chiral selector in capillary zone electrophoresis in a study of the chiral separation of labetalol stereoisomers. Heptakis(2,3-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS-beta-CD) and octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin (ODAS-gamma-CD) were shown to be effective in separating labetalol stereoisomers. Optimal separating conditions of the four stereoisomers of labetalol were achieved with 10 mM HDAS-beta-CD and 10 mM ODAS-gamma-CD in an acidic pH buffer of low molarity. Data illustrating the effects of capillary length and cyclodextrin concentration on the separation are presented. The longer capillary length and high voltage enabled the baseline separation of all isomers in less than 15 min. The optimized method was applied to the analysis of human control plasma containing labetalol utilizing solid-phase extraction (SPE) in the 96-well format.