Hofmann-type rearrangement of imides by in situ generation of imide-hypervalent iodines(III) from iodoarenes

The Hofmann-type rearrangement of aromatic and aliphatic imides using a hypervalent iodine(III) reagent generated in situ from PhI, m-CPBA, and TsOH·H(2)O proceeded in the presence of a base in alcohol to provide anthranilic acid derivatives and amino acid derivatives in high yields, respectively. This reaction proceeds through a tandem reaction via alcoholysis followed by a Hofmann rearrangement promoted by the formation of an imide-λ(3)-iodane intermediate.     

A Novel Synthesis of 4‐Pyridazineacetic Acids via Ring Expansion of N‐Cyanomethylated 3‐Pyrazoline‐4‐acetic Acids

A novel synthetic route to 4‐pyridazineacetic acids 10 – 12 has been achieved by the ring‐expansion reaction of N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 – 9 . 1H‐Pyrazole‐4‐acetic acids 1 – 3 were reacted with iodoacetonitrile in the presence of triethylamine in refluxing acetonitrile to give the corresponding C‐cyanomethylated 1H‐pyrazole‐4‐acetic acids 4 – 6 as major products together with N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 and 8 as minor products. On the other hand, reactions of 1 and 3 with chloroacetonitrile in the presence of triethylamine in refluxing chloroform afforded the corresponding N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 and 9 as major products. Thermal treatment of 7 – 9 with sodium hydride in N,N‐dimethylformamide caused ring expansion to yield the corresponding 4‐pyridazineacetic acids 10 – 12 .     

Production and purification of organic reagents labeled with radioisotopes produced by an accelerator

We studied the production of nine typical organic analytical reagents labeled with¹¹C,¹³N and¹⁸F by irradiation with charged particles and bremsstrahlung and the purification of labeled compounds with HPLC and sublimation. As a result, we found that six reagents, α-naphthol, β-naphthol, quinoline, α-nitroso-β-naphthol, 8-hydroxyquinoline, and 1,10-phenanthroline H₂O could be labeled with¹¹C by bombarding a mixture of each reagent and boron with protons. More than 10% of the¹¹C was successfully exchanged with carbon atoms in the original reagents. We also found that sublimation is useful for purifying 8-hydroxyquinoline labeled with¹¹C. The extraction property of¹¹C-labeled 8-hydroxyquinoline between water and chloroform could be easily monitored by radioactivity measurement.     

Compositional plane of a wide-gap semiconductor CaCdSeS lattice-matched to InP and GaAs

We have investigated compositional plane of a wide band gap solid solution semiconductor Ca_1−xCd_xSe_1−yS_y (x0.32) using powder synthesis under thermal equilibrium condition. The solubility limit at 1273 K varies with respect to the Se concentration y, taking a minimum Cd solubility limit of 0.12 at y=0.8 and a maximum limit of 0.32 at y=1.0. It is found that the system can be lattice-matched to GaAs and InP under covering the energy band gap of ultraviolet–visible region. These results allow to design optoelectronic devices adopting the Ca_1−xCd_xSe_1−yS_y system.     

Mössbauer study of Fe−Zr amorphous alloys hydrogenated at different cathodic potentials

Mössbauer spectroscopy was used for studying the effect of hydrogenation on amorphous Fe₉₀Zr₁₀ and Fe₈₉Zr₁₁ alloys electrolytically charged to high hydrogen content. The differences observed between the room temperature Mossbauer spectra of uncharged and hydrogenated amorphous alloys can be attributed to a change in the Curie temperature. Up to a certain hydrogen content the Curie temperature increases with the hydrogen concentration while the Curie temperature goes thorough a maximum as the hydrogen content increases.     

Determination of localized states in porous silicon

We determined the density of state distribution near the Fermi level in porous silicon from the analysis of the current–voltage (J–V) and the current–thickness (J–T) characteristics in the space-charge-limited-current (SCLC) regime. The distribution exhibits a minimum density at the Fermi level, which is similar to the U-shape-trap-distribution observed in crystalline Si–SiO₂ interface or in amorphous Si. Theoretical analysis well explains both the J–V and the J–L characteristics, which implies that the current flow is entirely controlled by localized states situated at the quasi-Fermi level.     

Revaluation of the internal standard method coupled with the standard addition method applied to soil samples by means of photon activation

In order to achieve the highly accurate and precise multielement determination in environmental materials, the usefulness of the comparative standard provided by the processing method proposed previously for soil samples has been re-examined using calcareous loam soil, light sandy soil and river sediment as unknown samples. As a result, it was also demonstrated that concentrations of 15 trace elements in each sample can be determined effectively and reasonably.     

Mössbauer investigation of Fe−Zr amorphous alloys hydrogenated after annealing

Transmission and conversion electron Mössbauer spectroscopy were used in order to get further information bout thé effect of hydrogenation in Fe₈₉Zr₁₁ amorphous alloys in connection with the observation that the magnetically split spectrum appearing at room temperature due to a moderate hydrogenation gradually collapses with increasing hydrogen content. The Mössbauer measurements were performed on differently hydrogenated amorphous samples aged at 150 °C 300 °C and 600 °C before the hydrogenation. The time dependence of hydrogenation has also been measured. From the changes of Mössbauer parameters depending on the annealing temperature as well as on the cathodic potential of hydrogenation (compared with the hydrogen concentration measured by gas chromatography) we can conclude that relaxation processes and structural changes, taking place in these amorphous alloys, influence the hydrogen uptake, already at relatively low temperatures.