An unusual twist conformation of 2-O-methyl-1,3,4,5-tetrakis-O-tert-butyldiphenylsilyl-myo-inositol

The ring conformation of 2-O-methyl-1,3,4,5-tetrakis-O-tert-butyldiphenylsilyl-myo-inositol was in a twist form both in solid state and in solution. This is the first observation of a stable twist conformer induced by the introduction of bulky silyl protecting groups.     

Highly active, immobilized ruthenium catalysts for oxidation of alcohols to aldehydes and ketones. Preparation and use in both batch and flow systems

A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases.     

Crystal structure of poly(p-benzamide)

Redetermination of the crystal structure of poly(p-benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the N? C bond of the amide group and about the virtual bond of N-phenyl-C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P2₁2₁2₁-D. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc.     

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.     

Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

Summary The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. R_F values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm^–3 and 0.01–3 mol dm^–3, respectively, and are compared with those obtained with Avicel SF. R_F spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme R_F values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.     

Palladium-catalysed dimerization of vinylarenes using indium triflate as an effective co-catalyst

A palladium-indium triflate catalyst was found to be much more active for the dimerization of vinylarenes compared with generally used cationic palladium(II) catalysts.     

Liquid-phase hydration process of cyclohexene with zeolites

The liquid-phase hydration process of cyclohexene into cyclohexanol with zeolite is described. The characteristic of this industrial process is that fine particles of zeolite are used in a slurry system, which offers high productivity and a simple separation system. In this process, the hydrophobic property and shape selectivity of ZSM-5 are fully utilized so as to realize an economical industrial process.     

New approaches inμ + SR studies on critical phenomena in Ni

The critical phenomena in Ni are probed by pulsedSR method under longitudinal- and zero external magnetic fields. The sample magnetization around the critical temperature is confirmed simultaneously by bulk magnetization measurement in situ, disappearance of transverseSR signal and recovery of asymmetry under longitudinal field. At the same time, the ratio of the ⁺ hyperfine field to the bulk magnetization in the ferromagnetic phase below the critical temperature is determined from the observables obtained only in the present experiment. The zero- and low-field longitudinal relaxation rate of muon does not diverge in approaching toT _c in the paramagnetic region, but seems to reach a saturation value.This work is supported by the Grand-in-Aid of the Japanese Ministry of Education, Culture and Science.     

Release from or through a wax matrix system. V. Applicability of the square-root time law equation for release from a wax matrix tablet

To obtain basic and clear release properties, wax matrix tablets were prepared from a physical mixture of drug and wax powder at a fixed mixing ratio. Properties of release from the single flat-faced surface, curved side surface, and/or whole surface of the wax matrix tablet were examined. Then tortuosity and the applicability of Higuchi's square-root time law equation were examined. The Higuchi equation well analyzed the release processes of different release manners. However, the region fitted to the Higuchi equation differed with the release manner. Tortuosity obtained with release from the single flat-faced surface and curved side surface was comparable with that obtained with the release from a reservoir device tablet, whereas tortuosity obtained with release from the whole surface was larger. As the wax matrix tablets were prepared at a fixed mixing ratio, their internal structures should be similar. Therefore changes in the matrix volume or volume fraction with release were examined, and an extra volume where dissolved drug stray becomes large with release time in the case of release from the whole surface. These factors should be taken into account for evaluation of applicability and release properties. Furthermore, the entire release process should be analyzed using a combination of the square-root time law and other suitable equations in accordance with release manner or condition.     

Thermal behavior of ternary Sm2Fe17Nx magnets

The Mössbauer spectra of Sm₂Fe₁₇N_x, prepared by the nitrogenation of Sm₂Fe₁₇ powders in an ammonia and hydrogen atmosphere, were observed at elevated temperatures to shed light on the thermal behavior of nitrogen in the compounds Sm₂Fe₁₇N_x. It was found that there were large differences in thermal behavior between the starting Sm₂Fe₁₇, crystalline Sm₂Fe₁₇N_x (x≈1.7) and amorphous Sm₂Fe₁₇N_x(x～7). The thermal decomposition behavior of Sm₂Fe₁₇N_3.2, developed as one of the most promising hard magnetic materials, was found to be different under different atmospheres.