Reductive carbonylation of nitrobenzene over Pd/Fe/I2/Py and Pd/C/Fe/I2/Py catalytic systems

A simple catalytic system containing metallic palladium, iron and iodine has been shown to be very active in the carbonylation of nitrobenzene to carbamate. The influence of the components of the catalytic system studied on its selectivity and activity has been established. It has been found that the catalytic activity of palladium supported on carbon (using both lignite coal and bituminous coal) was not lower than the activity of metallic palladium. This revised version was published online in August 2006 with corrections to the Cover Date.     

New analogs of temporin-LK1 as inhibitors of multidrug-resistant (MDR) bacterial pathogens

The peptide temporin-LK1 (1) was obtained from the skin secretion of frog Limnonectes kuhlii (Ranidae). It is a unique antimicrobial peptide with 17 residues, including four L-phenylalanines and single glycine. Mass spectrometry and Edmand degradation were used for the determination of sequence of amino acids in temporin-LK 1 (1), and confirmed by cDNA cloning. We report here the synthesis and structural studies of temporin-LK1 (1) and its analogs 2–4. Peptides 2–4 were prepared by substitution of achiral glycine residue of temporin-LK1 (1) with D-alanine, L-phenylglycine, and L-naphthylalanine, respectively. Peptides 1–4 were evaluated against multidrug-resistant (MDR) strains of Staphylococcus aureus and Pseudomonas aeruginosa. Analog 2 was found active against all MDR strains of S. aureus and P. aeruginosa at a much lower dose than the clinically used antibiotics.     

The reactions of phenolic reagents with α-bromo Michael acceptors in the K2CO3-acetone system. A stereospecific AdSNE process.

α-bromo Michael acceptors undergo ipso-substitution by phenol or benzenethiol in the K₂CO₃-acetone system, the reaction originating the (Z) isomers, via a stereospecific Ad_SNE process.     

Determination of cefotaxime and desacetylcefotaxime in cerebrospinal fluid by solid-phase extraction and high-performance liquid chromatography

A microfluidic analytical system for the separation and detection of organic peroxides, based on a microchip capillary electrophoresis device with an integrated amperometric detector, was developed. The new microsystem relies on the reductive detection of both organic acid peroxides and hydroperoxides at -700 mV (vs. Ag wire/AgCl). Factors influencing the separation and detection processes were examined and optimized. The integrated microsystem offers rapid measurements (within 130 s) of these organic-peroxide compounds, down to micromolar levels. A highly stable response for repetitive injections (RSD 0.35-3.12%; n = 12) reflects the negligible electrode passivation. Such a "lab-on-a-chip" device should be attractive for on-site analysis of organic peroxides, as desired for environmental screening and industrial monitoring.     

Nucleophilic substitution of α-halo-ketones. XXIII. Acetolysis of 1-chloro-3-phenoxy-1-phenylthio-2-propanones. An intramolecular trans-acetylation involving phenoxide anion as the leaving group

The acetolyses of α-chloro-ketones1a-c,2a-c,9a and11a have been investigated parallely. Several aspects of the mechanisms involved in chlorine normal and cine substitution have been elucidated. Intramolecular trans-acetylation, ultimately leading to fragmentation of acetoxy-ketones3b,4a and4c, have been postulated to account for the formation of thiol ester6, aldehyde5a and ketone5c, respectively.     

Adsorption of thiourea on mercury in water + methanol mixtures

The adsorption of thiourea on mercury has been investigated by capacitance measurements in three water + methanol mixtures, having various mole fractions of methanol.The back integration method was employed to obtain the curves of surface charge densities at the mercury surface for different concentrations of thiourea in the solution.As a test of specific adsorption in the systems studied the Esin-Markov plots were used.     

Polarographic studies on the complexation of cobalt(II), nickel(II) and copper(II) withd-glucosamine andd-galactosamine

D.c. polarography was used to establish the equilibria existing in Cu(II), Ni(II) and Co(II) systems with d-glucosamine and d-galactosamine. The results clearly indicated the formation of 1:1 complexes, ML, and allowed calculation of the stability constants of some complexes. The present results completed very well the potentiometric and spectroscopic data obtained earlier. The reduction mechanisms and the electrochemical behaviour of the formed complexes were also established.     

Studies of the mixed adsorption layer on a mercury electrode in the systemp-toluidine-polyethyleneglycol-1M NaClO4

Summary The properties of the mixed adsorption layer on a mercury electrode in the system 1M NaClO₄-p-toluidine-polyethyleneglycol (average molecular masses of polyethyleneglycols: 400 or 10000) are discussed. The parameters of theFrumkin and virial isotherms were determined in the range of strong adsorption potentials. In the range of more negative potentials, a mixed adsorption layer was found by investigating the kinetics of the reduction of Zn(II) ion as a pilot ion. Depending on the concentration ratio of the studied organic substances, inhibition, acceleration, or compensation of both with respect to Zn(II) electroreduction was observed. In the presence of polyethyleneglycol, the efficiency of the Zn(II) ion electroreduction increases due to a greater adsorption lability ofp-toluidine molecules on the mercury surface.

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Untersuchung der gemischten Adsorptionsschicht an einer Quecksilberelektrode im Systemp-Toluidin-Polyethyleneglycol-1M NaClO₄

Zusammenfassung Die Eigenschaften der gemischten Adsorptionsschicht an einer Quecksilberelektrode trode im System 1M NaClO₄-p-Toluidin-Polyethyleneglycol(durchschnittliche Molmassen der Polyethylenglycole: 400 bzw. 1000) werden diskutiert. Die Parameter derFrumkin- und Virialisotherme wurden im Bereich hoher Adsorptionspotentiale bestimmt. Im Bereich negativerer Potentiale wurde durch Untersuchung der Kinetik der Elektroreduktion von Zn(II)-Ionen als Pilotionen eine gemischte Adsorptionsschicht gefunden. In Abhängigkeit von der Konzentration der organischen Verbindungen beobachtet man bezüglich der Elektroreduktion von Zn(II) Hemmung, Beschleunigung oder eine gegenseitige Kompensation beider Effekte. In Gegenwart von Polyethyleneglycol nimmt die Effizienz der Elektroreduktion von Zn(II) aufgrund einer höheren Adsorptionslabilität derp-Toluidin-Moleküle an der Quecksilberoberfläche zu.

     

New SRDN-3 probes with a semi-conductor detector for measuring radon activity concentration in underground spaces

The article presents new Polish probes SRDN-3, developed at the Institute of Nuclear Chemistry and Technology in Warsaw, equipped with a semi-conductor detector used for continuous measurements of ²²²Rn activity concentration. Due to a relatively high lower detection limit, the device is dedicated for use in underground spaces—caves, adits, mines, tourist routes in strongholds, pyramids, etc. Its structure allows for difficult conditions in which the device is transported to the measurement site, as well as hard operating conditions caused chiefly by large ambient relative humidity, reaching up to 100%. The authors present calibration results of these appliances, as well as the results of their work in a cave and an adit in the Sudetes (SW Poland). After almost 2 years of working in difficult conditions, the probes displayed high reliability. No defects of the semi-conductor detectors or the electronics were observed, which ensured problem-free communication of the probe-programmer-PC set. Thanks to this, the authors have a 2 year stock of data, recorded hourly by five probes, at their disposal. The only element that did not withstand the test of extreme operating conditions was one of the combined relative humidity and temperature sensors. No powering problems were observed either, and the batteries were replaced once a year, before the winter season. Also the programmer functioned faultlessly, enabling data transmission to a PC, which, being much more sensitive to operating conditions, had been placed away from the site of probe exposure. After using more sensitive temperature, relative humidity and pressure sensors, SRDN-3 probes will certainly prove an excellent tool for microclimate measurements (including measurement of air-atmosphere exchange) in caves and other underground sites. Even nowadays they are already a satisfactory tool for monitoring ²²²Rn concentration in underground spaces.