N‐bromosuccinimide catalyzed condensations of indoles with carbonyl compounds under solvent‐free conditions

NBS was found to be an efficient catalyst for condensations of indoles with aldehydes or ketones in the absence of solvent.     

Determination of traces of iron with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse polarographic method for the determination of iron employing the catalytic maximum wave has been studied. A well-defined differential pulse polarographic peak for iron(III) in Britton-Robinson buffer solution containing 50 mol/l N-(2-hydroxyethyl) ethylenediamine N,N,N-triacetic acid (HEDTA) and 5 mmol/l KBrO₃ is observed in the potential range from +0.2 to –0.3 V vs. SCE. The peak current is very large compared to that of the Fe(III)/EDTA complex, being proportional to the concentration of iron(III) between 1.00×10^–8 and 3.58×10^–6 mol/l under optimum conditions. The relative standard deviations for 3.58×10^–7 mol/l and 1.79×10^–6 mol/l iron(III) were 1.38 and 0.54%, respectively (n=5), and the calculated detection limit was 5.2×10^–9 mol/l iron(III). The method has been applied to the determination of iron in fresh snow and rain waters.

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Spurenbestimmung von Eisen mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Das Verfahren beruht auf der Tatsache, daß in Britton-Robinson-Puffer (mit 50 mol/l HEDTA und 5 mmol/l KBrO₃) im Potentialbereich von +0,2 bis –0,3 V gegen SKE ein gut definierter puls-polarographischer Peak für Eisen(III) auftritt. Der Peakstrom ist im Vergleich zu dem des Fe(III)/EDTA-Komplexes sehr groß und ist unter optimalen Bedingungen im Konzentrationsbereich von 1,00·10^–8 bis 3,58·10^–6 mol/l der Eisen(III)-Konzentration proportional. Die relative Standardabweichung beträgt 1,38% bzw. 0,54% (n=5) für 3,58·10^–7 mol/l bzw. 1,79·10^–6 mol/l Fe(III). Die berechnete Nachweisgrenze liegt bei 5,2·10^–9 mol/l Fe(III). Das Verfahren wurde zur Eisenbestimmung in Schnee- und Regenwasser eingesetzt.

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This work was supported in part by a Grant-in-Aid for Scientific Research from Hokkaido-prefecture, 1982.     

Radiometric analysis based on redox substoichiometry I. Principles and application for the determination of tellurium

A radiometric method based on the redox substoichiometry has been developed for the determination of tellurium. The oxidation of tellurium(IV) to tellurium(VI) with potassium dichromate was employed as the substoichiometric reaction, followed by TBP (tributyl phosphate) extraction of the unreacted tellurium(IV) as the substoichiometric isolation. The oxidation of tellurium(IV) with dichromate under the substoichiometric conditions was incomplete. The chemical yield of tellurium(VI) produced by the oxidation of tellurium(IV) with dichromate was 83%. It was found that a tellurium content of 50 to 160 g could be determined with an accuracy of ±1.3% by means of the comparison method.     

Superhigh-Rate Epitaxial Silicon Thick Film Deposition from Trichlorosilane by Mesoplasma Chemical Vapor Deposition

Homoepitaxial Si thick films have been deposited by mesoplasma chemical vapor deposition (CVD) with SiHCl₃ (TCS)–H₂–Ar gas mixtures. The addition of a small amount of H₂ has been found to not only modify the film structure from polycrystalline to epitaxial but also effectively improve the deposition efficiency and film purity by removing Cl in the form of HCl. However, an excess introduction of H₂ decreases the deposition efficiency owing to the shrinkage of the plasma flame. On the other hand, an increase in TCS flow rate increases the epitaxial deposition rate despite exhibiting a saturating tendency, while the material yield tends to decrease gradually due possibly to an increase in the Cl atoms. Also, we observed a critical limit in the TCS flow rate for epitaxial growth, beyond which a polycrystalline film resulted. However, when RF input power was increased, not only the upper limit of TCS flow rate for epitaxy was extended but also the deposition yield was improved so that the deposition rate reached ~700 nm/s with the material yield of >50 % at 30 kW input power with an H₂/TCS ratio of 1.5. Additionally, high input power is found to be beneficial to decrease Cl atom incorporation into the film and improve the Hall mobility of the films. An epitaxial film with a Cl atom concentration of less than 3 × 10¹⁶ cm^?3 and a Hall mobility as high as 250 cm²/(V·s) was obtained at 30 kW input power.     

Inclusion complexes of melatonin with modified cyclodextrins

The solubility of melatonin (MT) was improved with the addition of modified cyclodextrins (CDs). The solubilities of MT in the presence of β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), mono-6-O-maltosyl-β-cyclodextrin (mono-G₂-β-CD), methyl-β-cyclodextrin (Me-β-CD), and sulfobutylether-β-cyclodextrin (SBE-β-CD) were higher than that of MT itself. In particular, the solubility of MT in the presence of SBE-β-CD was 11 times higher than that of MT itself. The stability constant (K) obtained based on the fluorescence intensity was 490 L/mol for the MT/SBE-β-CD inclusion complex. The structure of the MT/SBE-β-CD complex in aqueous solution was examined by ¹H–¹H rotating frame nuclear overhauser effect spectroscopy NMR. A 5-methoxy moiety of MT was included from the secondary hydroxyl face of SBE-β-CD. The MT/SBE-β-CD inclusion complex was prepared by the freeze-drying method. The results of X-ray diffraction and differential scanning calorimetry confirmed the formation of the complex in solid.     

Performance of fixed and fluidized bed reactors with immobilized enzyme

Applied Biochemistry and Biotechnology - Saccharification of α-amylase liquefied cassava starch was carried out at pH 4.5 and 45?C, in both fixed and fluidized bed reactors, using...