Perfluormethyl-element-liganden XXVlI [1] Darstellung und spektroskopische untersuchung von W(CO)5L-komplexen (L = R2EER′2, R2EE′R; R,R′ = CH3; CF3; E = P,As; E′ = S,Se, Te)

W(CO)₅L complexes (L = R₂EER′₂, R₂EE′R; R, R′ = CH₃, CF₃; E = P, As; E′ = S, Se, Te) have been prepared by reaction of W(CO)₅·THF with L at room temperature or by redistribution reaction of W(CO)₅E₂Me₄ with E₂(CF₃)₄ or E′₂Me₂ as well as by cleavage of E₂(CF₃)₄ with W(CO)₅EMe₂H. The new compounds were characterized by analytical and spectroscopic (IR, NMR, MS) methods; by comparison with of the data of free and coordinated ligands the effects of complexation are studied.     

Some physical properties of compacted specimens of highly dispersed boron carbide and boron suboxide

Structure, shear modulus and internal friction (IF) of compacted specimens of boron carbide and boron suboxide have been investigated. Microtwins and stacking faults were observed along the {100} plane systems of polycrystalline specimens of boron carbide. Electrical conductivity of the specimens was that of p-type. Concentration of holes varied from 10¹⁷ to 10¹⁹ cm⁻³. The IF was measured in the temperature range 80-300 K. It was shown that the IF of boron carbide and that of boron suboxide were characterized with a set of similar relaxation processes. Mechanisms of the relaxation processes in boron carbide and boron suboxide are discussed in terms of the Hasiguti model of interaction between dislocations and point defects.     

Monofluorinated di- and tetrahydropyrans via Prins-type cyclisations

The synthesis of a range of fluorinated heterocycles is described via a Lewis acid-mediated Prins-type cyclisation.     

Photoelectron spectra and electronic structure of some 4-substituted 2-allylanisoles

The electronic structures of 4-substituted 2-allyl anisoles (1-9) have been investigated by ultraviolet photoelectron spectroscopy and quantum chemical methods. The ionisation potentials corresponding to the pi MOs pi(2) and pi(3) of the phenyl ring, and the n(O) orbital of the methoxy group as well as the allylic pi(C=C) orbital could be determined and assigned for 1-9. Linear regression analyses of the IPs related to these orbitals with different substituent constants indicated that Hammett sigma(p) values performed satisfactorily to fair for pi(2), pi(3) and n(O) but poor for allylic pi(C=C). Other substituent constants such as R and R(-) were fair only for pi(2) and pi(3), but poor for n(O) and pi(C=C).     

Role of convection and diffusion in a single pore with adsorptive walls

The importance of intraparticle convection during and after the pressurization step of a pressure swing adsorption process is assessed by considering a single, cylindrical, closed-end pore with adsorptive walls exposed to a binary mixture of an adsorbable component and an inert gas. Gas-phase mass transfer is comprised of pore diffusion and convection, and surface diffusion occurs in the adsorbed phase. Concentration, velocity, and flux profiles are obtained inside the pore both during and after pressurization. Solutions are obtained analytically for the limiting cases of no adsorption, no diffusion, and no inert gas. Complete solutions of the material balance equations are obtained by orthogonal collocation. The pressurization rate, the adsorptive capacity of the pore wall, and the gas-phase mole fraction are varied over a wide range to study the relative importance of convection and diffusion under different conditions. Results show that convection makes a large contribution to transport in the pore except when the adsorbable component has a small mole fraction.     

Quasi-classical approach: Electronic structure of cubic boron nitride crystals

Using the new version of the quasi-classical parameterization based on the screened Coulomb-like atomic potentials the band structure and the unit cell total energy are obtained for boron nitride cubic crystal (c−BN). The calculated density of electron states of the upper valence and lower conduction bands reveals that c−BN is an insulator with band gap of . The quasi-classical estimation of lattice constant is found to be a=3.588 Å.     

Alkyl, unsaturated, (hetero)aryl, and N-protected alpha-amino ketones by acylation of organometallic reagents

Stable and easily accessible N-acylbenzotriazoles, derived from a variety of aliphatic, unsaturated, (hetero)aromatic, and N-protected alpha-amino carboxylic acids, were reacted with Grignard and heteroaryllithium reagents to afford corresponding ketones in good to excellent yields.     

On some new modulation effects in magnetic resonance

Two new modulation effects are considered: the appearance of relaxation oscillations of Zeeman and dipole magnetizations in nuclear and electron paramagnets, and the manifestation of modulation in the spin-echo signals of nuclei in domain walls of magnets.     

A non-spectral representation of shift semigroups

A non-spectral representation of a continuous shift overL ²(0, ∞) is presented, using an interplay between the semigroup, its associated discrete shift operator and the shifted orthonormal basis generated by the latter.