15N-NMR Spectra of Azoles with Two Heteroatoms

The ¹⁵N-NMR spectra of azoles, with natural isotope abundance, have been measured under different experimental conditions, and chemical shifts are reported for imidazoles, pyrazoles, oxazoles, isoxazoles, thiazoles, and isothiazoles. General trends of substituent effects in this heterocyclic series are discussed based on the data of 67 substituted azoles, dihydro- and tetrahydroazoles. ¹⁵N, ¹H spin-coupling constants have been determined from spectra obtained by [¹H] → ¹⁵N polarizationtransfer experiments, i.e. an application of INEPT and DEPT pulse sequences. Two-bond and three-bond coupling constants are fully assigned and are discussed in terms of the specific pathways in azoles. The potential of structural applications of the new data is illustrated for isomeric nitro-imidazoles and highly-substituted pyrazoles, and in the case of ring-chain tautomerism of 2-substituted tetrahydrooxazoles.     

The synthesis of β-carboline derivatives-II A synthesis of some benz-indolo[2,3-a]pyridocolinium salts, including sempervirine

A novel synthetic method for β-carboline derivatives, described in the preceding paper, is now applied to the syntheses of 6,7-dihydro-12H-benz[f]indolo[2,3-a]pyridocolinium salt, 8,9-dihydro-14H-benz[h]indolo-[2,3-a]pyridocolinium salt and sempervirine. In the course of synthesis of sempervirine, 2-[2-(3-indolyl)ethyl]-3-chloro-5,6,7,8-tetrahydro-isoquinolinium bromide is obtained as an intermediate, lending strong support for the mechanism previously proposed.     

Functional Modification of Cellulose Acetate Microfiltration Membranes by Supercritical Solvent Impregnation

This study investigates the modification of commercial cellulose acetate microfiltration membranes by supercritical solvent impregnation with thymol to provide them with antibacterial properties. The impregnation process was conducted in a batch mode, and the effect of pressure and processing time on thymol loading was followed. The impact of the modification on the membrane’s microstructure was analyzed using scanning electron and ion-beam microscopy, and membranes’ functionality was tested in a cross-flow filtration system. The antibiofilm properties of the obtained materials were studied against Staphyloccocus aureus and Pseudomonas aeruginosa, while membranes’ blocking in contact with bacteria was examined for S. aureus and Escherichia coli. The results revealed a fast impregnation process with high thymol loadings achievable after just 0.5 h at 15 MPa and 20 MPa. The presence of 20% of thymol provided strong antibiofilm properties against the tested strains without affecting the membrane’s functionality. The study showed that these strong antibacterial properties could be implemented to the commercial membranes’ defined polymeric structure in a short and environmentally friendly process.     

Donor–Acceptor Interactions Induced Interfacial Synthesis of an Ultrathin Fluoric 2D Polymer by Photochemical [2+2] Cycloaddition

Two-dimensional polymers (2DPs) have attracted much interest due to their unique 2D atomic-thick covalent network with periodically linked monomers. The preparation of mono- or few-layered 2DPs with highly ordered structures is still a big challenge. Herein, we report a preparation of ultrathin 2DP film based on photo-triggered [2+2] cycloaddition at the air/water interface. The pre-assembly process induced by the D–A interactions before the polymerization plays a key role in constructing the highly ordered structure. The precise structure and chemical compositions of the continuous 2DP films were proved by selected area electron diffraction (SAED), Tip-Enhanced Raman Spectroscopy (TERS) and molecular-mechanics-based structural simulation.     

Reaction Mechanism of One-Step Conversion of Ethanol to 1, 3-Butadiene over Zn-Y/BEA and Superior Catalysts Screening

The one-step conversion of ethanol to 1, 3-butadiene has achieved a breakthrough with the development of beta zeolite supported dual metal catalysts. However, the reaction mechanism from ethanol to butadiene is complex and has not yet been fully elucidated, and no catalyst screening effort has been done based on central metal atoms. In this work, density functional theory (DFT) calculations were employed to study the mechanism of one-step conversion of ethanol to butadiene over Zn-Y/BEA catalyst. The results show that ethanol dehydrogenation prefers to proceed on Zn site with a reaction energy of 0.77 eV in the rate-determining step, and the aldol condensation to produce butadiene prefers to proceed on Y site with a reaction energy of 0.69 eV in the rate-determining step. Based on the mechanism revealed, six elements were selected to replace Y for screening superior combination of Zn-M/BEA (M=Sn, Nb, Ta, Hf, Zr, Ti; BEA: beta polymorph A) for this reaction. As a result, Zn-Y/BEA (0.69 eV) is proven to be the most preferring catalyst compared with the other six ones, and Zn-Zr/BEA (0.85 eV), Zn-Ti/BEA (0.87 eV), and Zn-Sn/BEA (0.93 eV) can be potential candidates for the conversion of ethanol to butadiene. This work not only provides mechanistic insights into one-step catalytic conversion of ethanol to butadiene over Zn-Y/BEA catalyst but also offers more promising catalyst candidates for this reaction.     

Plasma modified polymers as a support for enzyme immobilization 1.: Allyl alcohol plasma

The paper describes deposition of plasma polymerized allyl alcohol on polysulfone film. It is shown that film surface becomes more hydrophilic after plasma treatment independently on presence of argon in a reaction mixture. The chemistry of the new surface layer was established by FTIR-ATR and ESCA spectroscopy. The substrate placed close to the plasma edge was the most hydrophilic but the amount of hydoxyl groups was not the highest there. Presence of argon stabilized the plasma but the deposited layer contained relatively less oxygen-bearing functionalities. The plasma treated polymer was subjected to xylose isomerase immobilization. For this purpose the divinylsulfone method was adapted. The studies revealed no correlation between the surface hydrophilicity and efficiency of immobilization.     

Thiol–thione tautomeric forms recognition on the example of 4‐[3‐(2‐methyl‐furan‐3‐yl)‐5‐thioxo‐1,2,4‐triazolin‐4‐yl]acetic acid

The synthesis of 4‐[3‐(2‐methyl‐furan‐3‐yl)‐5‐thioxo‐1,2,4‐triazolin‐4‐yl]acetic acid, its structural study in the solid state, and the thiol–thione tautomeric recognition on the basis of spectroscopic data and theoretical calculations are presented. It is shown that NMR spectra, especially ¹³C and ¹⁵N, are indicative of the actual tautomeric form whereas vibrational data can be ambiguous. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:337–344, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20433     

Elektrische Leitfähigkeitsänderungen bei der Festkörperreaktion

The equation describing changes in the electric conductivity (measured by the dc method) of a mixture of powdered reactants undergoing solid state reactions which fulfill some assumptions was derived. The equation depicts the temperature dependence of the specific electric conductivity at a linear increase of temperature as a function of electric conductivities of reagents and the reaction product (which also depend on temperature), as well as kinetic parameters. The following assumptions were made: statistically distributed close-packed ball-shaped identical grains are flattened in places of contact, and the reaction proceeds without intermediate products, by the mechanism of counterdiffusion through the product layer. Changes in the electric resistivity of grains on increasing the thickness of the product layer were considered. The specific electrical conductivity of the system grains was given. The effect of the process on additional defecting of the product layer was taken into consideration.     

Measurement of the CP asymmetry in B-->Xs gamma

Direct CP violation in the b-->sgamma process is a sensitive probe of physics beyond the standard model. We report a measurement of the CP asymmetry in B-->X(s)gamma, where the hadronic recoil system X(s) is reconstructed using a pseudoreconstruction technique. In this approach there is negligible contamination from b-->dgamma decays, which are expected to have a much larger CP asymmetry. We find A(CP)=0.002+/-0.050(stat)+/-0.030(syst) for B-->X(s)gamma events having recoil mass smaller than 2.1 GeV/c(2). The analysis is based on a data sample of 140 fb(-1) recorded at the upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring.