N,C10-Überbrückte Morphinalkaloide, 5H-10,13-Iminoethano-phenanthro[4,5-bcd]furan, 2. Mitt.

Summary Following our concept of rather new structural variations in the nitrogen region of morphine alkaloids we describe the first synthesis of N/C-10-bridged tertiary bases.

     

Dimerization of some substituted benzoic acids in aqueous solution from conductance measurements

Precision molar conductances of benzoic, o-toluic, 2,6-dimethylbenzoic, 2,3,6-trimethylbenzoic, and, o-fluorobenzoic acids have been determined in aqueous solution as a function of temperature and of concentration up to near saturation (<0.035 M). At the higher concentrations molar conductances are found to be less than anticipated for the simple dissociation of a 1-1 electrolyte. Although the deviations are only 1% or less they have been interpreted to show that these acids are dimerized in solution. The interpretation includes an assumption that the dimer ionizes to produce a triple ion. Increasing numbers of methyl groups lead to increasing dimerization. For those acids with two ortho groups the dimerization increases with increasing temperature while the other three show decreasing dimerization with increasing temperature. Temperature functions have been determined for the dimerization constants and from these functions standard changes in enthalpy, entropy, and heat capacity have been determined. Comparisons are made with dimerization studies in non-aqueous solvents. From these as well as the behavior of benzene in water it is concluded that a major factor driving the dimerization is hydrophobic interaction. To provide a limiting conductance of the triple ion needed in the dimerization calculations a conductance study was also made for o-Phenylbenzoic acid on the assumption that its anion provides an approximate model of the triple ion.     

Properties of ITO films prepared by reactive magnetron sputtering

Indium tin oxide (ITO) thin films were deposited by mid frequency pulsed dual magnetron sputtering using a metallic alloy target with 10 wt.% tin in an atmosphere of argon and oxygen. The aim of the work was to study the interdependence of structural, electrical and optical properties of ITO films deposited in the reactive and transition target mode, respectively. The deposition rate in the transition mode exceeds the deposition rate in the reactive mode by a factor of six, a maximum value of 100 nm·m min⁻¹ could be achieved. This corresponds to a static deposition rate of 200 nm min⁻¹. The lowest electrical resistivity of 1.1·10⁻³ Ω cm was measured at samples deposited in the high oxygen flow range in the transition mode. The samples show a good transparency in the visible range corresponding to extinction coefficients being below 10⁻². X-ray diffraction was used to characterise crystalline structure as well as film stress. ITO films prepared in the transition mode show a slightly preferred orientation in (211) direction, whereas films deposited in the reactive mode are strongly (222) oriented. Compared to undoped In₂O₃ all samples have an enlarged lattice. The lattice strain perpendicular to the surface is about 0.8% and 2.0% for films grown in the transition and the reactive mode, respectively. Deposition in the transition mode introduces a biaxial film stress in the range of −300 MPa, while stress in reactive mode samples is −1500 MPa.     

Efficient synthesis of enynecarbamates and their ring-closing metathesis/[4 + 2] Diels-Alder cycloaddition: synthesis of hexahydroisoquinolines

Enynes 5a-g were prepared in moderate to good yields from 1-(triphenylphosphoranylideneaminoalkyl)benzotriazoles. Ring-closing metathesis of 5a-f afforded functionalized dienes 6a-f, respectively, which were used in a Diels-Alder cycloaddition reaction in the synthesis of the corresponding hexahydroisoquinoline derivatives 7a-f.     

Lithiation and electrophilic substitution of 8-chlorodibenz[b,f][1,4]-oxazepine-10-tert-butylcarbamate: The preparation of novel fused heterocyclic derivatives of 8-chlorodibenzoxazepine

Lithiation of 8-chlorodibenz[b,f][1,4]oxazepine-10-tert-butylcarbamate ( 1 ) is described. Electrophilic substitution of the resulting N-Boc dibenzoxazepine α- lithioamine 2 with ketones, aldehydes, nitriles, iso-cyanates and imines, followed by an in-situ cyclization, gave fused carbamates 5–26 , fused 2H-imidazol-2-ones 27–29 , fused hydantoins 30–32 , and fused ureas 33–35 , respectively, in 11–66% yield.     

Investigation of gas chromatographic interaction mechanism on permethylated cyclodextrins by molecular modelling

Summary The capillary gas chromatographic retention behavior of -pinene and tricyclene has been investigated on stationary phases of different polarities. On all but one of the columns employed, tricyclene eluted before -pinene; only permethylated -cyclodextrins dissolved in moderately polar polisiloxanes gave a reversed elution order. The intermolecular interactions which caused the unexpected retention behavior were investigated in detail, applying methods of computer simulation. To achieve this, we have developed a calculation algorithm on the basis of molecular mechanical optimizations and programmed it in a macro. This makes it possible to systematically investigate a given configuration space in which all the possible interactions can take place. It was shown that permethylated -cyclodextrin as host molecule for both guest molecules offers an optimum cavity size. As a result the number of energetically favorable contacts between host and guest molecules as well as the strength of the interactions in this stationary phase were larger. As a consequence the elution order, normally only influenced by the vapor pressure of the compounds at a given temperature, was changed. Nonspecific interactions played an especially important role for these kinds of substances.     

Femtosecond intermolecular electron transfer in condensed systems

We have investigated the ultrafast intermolecular electron transfer (ET) from an electron-donating solvent (aniline (AN) or N, N-dimethylaniline (DMA)) to an excited dye molecule (oxazines (Nile blue and oxazine 1) or coumarins). A non-exponential time dependence was observed in AN and can be explained by solvent reorientation and nuclear motion of the reactants. However, in DMA, a single exponential process was observed for Nile blue (160 fs) and oxazine 1 (280 fs), which can be explained by assuming that the rate of ET is limited mainly by ultrafast nuclear motion. A clear substituent effect on intermolecular ET was observed for the 7-aminocoumarins. When the alkyl chain on the 7-amino group is extended and a hexagonal ring with the benzene moiety is formed, the rate of ET is reduced by three orders of magnitude. This effect can be explained by a change in the free energy difference of the reaction and by the vibrational motion of the amino group.     

Supercritical fluid chromatography of industrial paraffins and waxes

Summary The application of capillary SFC for SIMDIST investigations of paraffins and waxes is reported. Pressure, density and temperature of the mobile phase are optimized to obtain high chromatographic resolution of complex mixtures of industrial products. Isothermal linear pressure programming and asymptotic pressure and density programming are used in the range from 15 to 35 MPa in the isothermic mode above 100°C. SFC chromatograms of natural and synthetic paraffins, microcrystalline wax and candle wax are compared. The retention behaviour of paraffin mixtures and waxes has been investigated on methyl/phenyl and biphenyl capillary columns. The polarity of the stationary phases influences the absolute retention time more than it influences the chromatographic resolution.     

A single crystal study of eight-layer barium managanese oxide,BaMnO3

A single crystal study of hydrothermally prepared eight-layer BaMnO₃ has been carried out which confirms the (Zhdanov notation) 121121 layer stacking scheme for the BaO₃ layers. The MnO₆ octahedra share faces in strings of four, and these strings are connected to each other by corner sharing. The compound has an hexagonal unit cell of dimensions a = 5.667 ± 0.003 and c = 18.738 ± 0.009 Å, probable space group $\text{P6}{}_3\text{mmc}\text{, Z = 8}$. Its structure has been determined from 352 independent reflections, of which 242 were considered observed, collected manually by a counter technique and refined to a conventional R value of 0.079.