Diphenylboron perchlorate as an efficient catalyst for self- and cross-condensation reactions of aldehydes having α-active hydrogens

Diphenylboron perchlorate very smoothly catalyzed self- and cross-condensation reactions of aldehydes at rt in nitroethane. The new catalyst provided novel behaviors owing to the characteristics of possessing a covalency in the boronoxygen bond, compared with ionic perchlorates.     

Resonance effect in solvolysis of 1-methylbenzyl chlorides

Substituent effects of p-MeO and p-MeS groups deactivated by additional m-substituents in cumyl and α-phenylethyl solvolyses were studied to provide evidence for the higher resonance demand in the α-phenylethyl system.     

Sufficient conditions for robust stability of large-scale dynamical systems including delayed states and parameter perturbations in interconnections

The problem of the robust stability of large-scale dynamical systems including delayed states and parameter perturbations in interconnections is considered. By using algebraic Riccati equations and some analytical methods, some sufficient conditions on linear decentralized state feedback controllers are derived so that the systems remain stable in the presence of delayed states and parameter perturbations. Such conditions give some bounds on the perturbations of interconnections with delayed states and uncertain parameters, and result in a quantitative measures of robustness for large-scale dynamical systems including delayed states and uncertain parameters in interconnections. The results obtained in this paper are applicable not only to large-scale systems with multiple time-varying delays, but also to large-scale systems without exact knowledge of the delays, i.e., large-scale systems with uncertain delays.     

Fluorescence-based assay with enzyme amplification on a micro-flow immunosensor chip for monitoring coplanar polychlorinated biphenyls

Detection of pollutants is of significant importance for environmental protection. However, conventional monitoring methods are often time-consuming, and require expensive equipments. Biosensors based on enzyme linked immunosorbent assay (ELISA) provide an alternative method to conventional ones. In this research, the reduction in the size of ELISA utilizing micro-chemical reaction is described in a micro-flow immunosensor chip. The immunosensor chips were fabricated by micro-electromechanical system (MEMS) technology. The quantitative determination of coplanar polychlorinated biphenyls (Co-PCBs) was performed by using a micro-flow immunosensor chip. Polystyrene beads were used as the solid substrate for the immobilization of Co-PCB antibody. The antibody-immobilized beads were introduced into the flow channel. As a competitive ELISA, sample solution mixed with horseradish peroxidase (HRP) conjugated antigen, and non-HRP conjugated antigen was allowed to react in the flow channel. After the antigen-antibody reaction, addition of phosphate buffer solution containing hydrogen peroxide and the fluorogenic substrate produced a fluorescent dye, which was monitored with the resulting change in the fluorescence intensity. By using our micro-flow immunosensor chip, it was possible to determine the sensing range of Co-PCB derivatives up to 0.1 ppt in 30 s. This immunosensor chip had a wide linear range for Co-PCB detection from 0.1 pg/ml to 1.0 μg/ml. The regression analysis provided the correlation coefficients of r = 0.982−0.964 with good reproducibility and precision. In a series of five measurements with immunosensor chips prepared with a new batch of antibody-immobilized polystyrene beads, a relative standard deviation of 21.3% was obtained. Our immunosensor chip design reported here has the potential to be implemented to several different detection methodologies for numerous analytes.     

Concurrent induction of two chiral centers from symmetrical 3, 4-disubstituted and 3,3,4-trisubstituted 4-pentenals using Rh-catalyzed asymmetric cyclizations

Asymmetric cyclization of symmetrical 3,4-disubstituted and 3,3, 4-trisubstituted 4-pentenals was studied using Rh-complexes with chiral ligands. The cyclization of symmetrical 4-pentenals 4a,b by a neutral Rh[(R)-BINAP]Cl afforded cis-3,4-disubstituted (4R)-cyclopentanones 9a,b of >95% ee in 25-31% yields; on the other hand, the cyclization of 4a-c by a cationic Rh[(R)-BINAP]ClO(4) afforded trans-3,4-disubstituted (4S)-cyclopentanones 10a-c of >95% ee in 70-81% yields. All stereoisomers could be stereoselectively made by the selection of a neutral or cationic Rh-complex, and (R)- or (S)-BINAP ligand. The Rh-catalyzed cyclization could be applied to the construction of cyclopentanones 17 and 18 bearing a chiral quaternary carbon. The cyclization by the cationic Rh[(R)-BINAP]ClO(4) afforded the optically active trans-3,3, 4-trisubstituted cyclopentanones 18a-c of 92-95% ee in 75-83% yields. The catalytic cycle was also studied by using deuterium aldehyde, and the tentative mechanisms of the enantio- and diastereoselection were proposed.     

Preparation of boron-doped semiconducting diamond films using BF3 and the electrochemical behavior of the semiconducting diamond electrodes

Boron-doped semiconducting diamond films were prepared using BF₃ by microwave plasma assisted chemical vapor deposition. B-doping was confirmed by SIMS and Raman spectroscopic measurements and the B-doping levels were estimated. Electrochemical behaviors of boron-doped diamond thin-film electrodes prepared using B₂H₆ and BF₃ were studied by measuring cyclic voltammograms for anodic oxidation of 1,4-difluorobenzene in the liquid electrolyte, neat Et₄NF·4HF. The results of the direct thermal interaction of elemental fluorine with hydrogenated and oxidized diamond surfaces are also presented.     

Synthesis of polybenzimidazoles with sulfonic acid groups

2-Sulfoterephthalic acid (STA) and disulfoisophthalic acid (DSIA) were synthesized through the sulfonation and the oxidation of m- and p-xylene. The polycondensation reactions of STA and DSIA with aromatic tetraamines gave polybenzimidazoles which contained one or two sulfonic acid groups for each repeating unit. The polymer obtained was soluble in sulfuric acid, some organic solvents, and aqueous strong alkaline solution. The polymers were stable up to 400°C, but they gave polybenzimidazoles above 400°C by eliminating sulfonic acid groups, instead of ring closure.     

Interference from electrostatic charges in the microdetermination of halogen and sulphur by the combustion method

Summary In the analysis of halogen and sulphur by the combustion method employing silver granules, electrostatic charges on the absorption funnel has been experimentally shown to cause inaccurate weighing of the funnel.An investigation of the influence of this phenomenon on blank values has been made, and possible countermeasures have been examined. By cooling the heated funnel in a desiccator saturated with moist air, the charges are removed and satisfactory analyses are obtained.

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Zusammenfassung Bei der analytischen Bestimmung der Halogene und des Schwefels durch Verbrennung und Bindung an Silbergranellen verursachen, wie gezeigt werden konnte, elektrostatische Aufladungen der Absorptionsgefäße Wägefehler. Untersuchungen über den Einfluß dieser Erscheinung durch Bestimmung von Leerwerten wurden ausgeführt und die Möglichkeit von Gegenmaßnahmen geprüft. Durch Abkühlen der heißen Absorptionsgefäße in einem mit feuchter Luft gefüllten Exsiccator lassen sich die Aufladungen beheben und richtige Analysenergebnisse erzielen.

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Résumé On a montré expérimentalement que dans l'analyse des halogènes et du soufre suivant la méthode de combustion avec granules d'argent, les charges électrostatiques sur le tube d'absorption étaient la cause d'une pesée inexacte de ce tube.On a fait une étude de l'influence de ce phénomène sur les valeurs à blanc et l'on a examiné la possibilité de mesures de l'éviter. En refroidissant le tube chauffé dans un dessicateur saturé d'air humide, on élimine les charges et l'on obtient des analyses satisfaisantes.