Effects of ultrasounds on electroorganic processes have extensively been examined in a series of investigations. The current efficiency and/or product selectivity were found to be greatly affected by ultrasonic irradiation. From experimental and theoretical considerations, it was verified that the effects are caused by mass transport enhanced by ultrasonic cavitation in the electrode interface. In addition, highly dense and uniform polymer films could be prepared by electrooxidative polymerization under ultrasonic irradiation. As a conclusion, it is stated that ultrasounds offer a powerful and useful method for purposive reaction control in a variety of electroorganic processes.

View full abstract

The molecular interaction of 1-methyl-2 (1H) -pyridinimine (1MPI), its methyl derivatives (1methyl-2 (1H) -pyridine (methyimine) (12MPMI), 1, 3-dimethyl-2 (1H) -pyridinimine (13DMPI), 1, 4-dimethyl-2 (1H) -pyridinimine (14DMPI), 1, 5-dimethyl-2 (1H)-pyridinimine (15DMPI) and 1, 6-dimethyl-2 (1H) -pyridinimine (16DMPI)), with iodine has been studied by UV, 1H-NMR and IR spectroscopies. The UV spectra of the above pyridinimines/iodine systems indicate that a 1: 1 charge transfer (CT) complex is formed between pyridinimines and I₂. The IR spectral results of these pyridinimines/iodine systems reveal that the new sharp band appears at ca. 1510 cm^-1 with increasing I₂ concentration in the CT complexes except for the 12MPMI/iodine and 13DMPI/iodine systems. The band. means that the interaction occurs at the nitrogen of the imino group of pyridinimines andthe I₂ molecule. The enthalpy change of complexation of the 15DMPI/iodine complex is the largest among specimens investigated to be 54.3 kJ mol^-1. On the other hand, the 12MPMI/iodine and 13DMPI/iodine systems make a weak interaction because the two methyl groups of the 12MPMI and 13DMPI keep away from the nitrogen of the imino group. In addition, from the NOESY spectral results the molecular structure of the CT complexes are discussed.

View full abstract

A method was developed for the synthesis of the complex perovskite solid solution of Sr(Cu_xZn_1-x)_1/2W_1/2O₃ (SCZW)having no compositional fluctuation. The method was a combination of wet and d ry processes. A very homogeneous powder mixture of CuO and ZnO (CZ-powder) was prepared by a decomposition of coprecipitate of Cu²⁺ and Zn²⁺ (wet process). Then CZ-powder and the other raw powders were mixed with an agate mortar and pestle (dry process). From this mixture, SCZW was synthesized with firing conditions of 1200 °C and 1 h. A compositional fluctuation in SCZW was studied through a measurement of angle dependence of width of X-ray powder diffraction peak. SCZW synthesized by this method had no compositional fluctuation.
SCZW synthesized by the conventional dry method (mixed-oxide method) had the compositional fluctuation. The compositional fluctuation decreased with an increase of the firing period. However, the fluctuation remained even when the sample was fired at 1200 °C for 4 h. This revealed that the compositional fluctuation cannot be easily eliminated by the dry method.
It was revealed that the compositional fluctuation i n SCZW results from the inhomogeneity of Cu²⁺ and Zn²⁺ in the raw powder mixture before firing. The fluctuation can be effectively eliminated by the application of wet process for a part of B-site cations, Cu²⁺ and Zn²⁺. This wet-dry combination method can be applied for many other solid solution of the type A^a+ ( B_I^b+_xB_II^b+_1-x) _dB_III^c+_1-dO₃ (a + bd + c ( 1-d ) = 6, b≠ c), because the number of cations to which the wet process is app lied can be reduced.

View full abstract

An effective method for the determination of thallium at ng/L levels in natural waters is d escribed. Thalluim is extracted with benzene as the diethyldithiocarbamate complex and subsequently baicnkt-ex-tracted into 0.2 mL of nitric acid. The back-extracted solution containing 50 mg/L of palladium as a matrix modifier is suitable for the determination of thallium by graphite furnace atomic absorption spectrometry. As the extractivity of thallium (III) was poorer than thallium (I), total thallium content was determined aftear rewdausction of thallium (III) with ascorbic acid. Wheh 700 mL of sample was used, the detection limit(3σ) was found to be 0.86ng/L of thallium in the initial soluthion based on a 2800-fold preconcentration. The relative standard deviation was 3.3% (20 ng/L, n=8). The proposed method is simple and rapid for the determination of ultra-trace amounts of thallium in natural waters. The dissolved thallium content in river water was 6.49 ng/L, and those in coastal sea waters were 13.4 and 15.3 ng/L.

View full abstract

The effect of microwave irradiation on Michael addition of β-dicarbonyl compounds (acetyl acetone, methyl acetoacetate, dimethyl malonate and diethyl ethylmalonate) to methyl vinyl ketone was investigated by using four different metal oxide catalysts, i. e., CaO, MgO, Al₂O₃ and SiO₂ without any solvent.
The microwave irradiation markedly accelerated the addition reaction, reducing the reaction ti me dramatically in comparison with the case of mechanical stirring (1/100-1/1500). The yields of the products were also moderately improved, and the values of the yield were dependent on the metal oxide catalysts. Thus, the order was well correlated with the partial charge on oxygen atom in metal oxide. This indicates that the more basicity due to larger partial charge on oxygen atom makes easier to extract proton at α-position of dicarbonyl compounds.

View full abstract

A new method has been developed for kinetic analysis of hydrothermal reactions to investigate chemical evolution of ribonucleic acid. The apparatus consists of a high pressure pump, a sample loop injector, a hydrothermal flow tube reactor, a cooling and back-pressure coil, and a sampling port and the samples are pumped to the hydrothermal tube reactor at constant flow rate for heating. Pressure in the hydrothermal flow tube reactor was regulated over the vapor pressure of water to keep the sample solution as liquid using an appropriate length of back-pressure coil. It was possible to monitor the consecutive hydrolysis of adenosine 5'-triphosphate (ATP) to hypoxanthine in the time rang of 0.4-140 s at 398-573 K and the rate constants for each step were determined by the computer program SIMFIT. Poly (tetrafluoroethylene) (PTFE) and stainless steel (SUS316) tubing have been examined for the hydrothermal flow tube reactor in which the apparent rate constants of ATP hydrolysis were in good agreement. The half life determined by the method was 0.31 s at 473 K for ATP and 0.42 s at 573 K for adenosine. This method enables real-time monitoring of model reactions of chemical evolution of RNA in aqueous solution at high temperatures.

View full abstract

Fe-C thin films have been prepared by electron shower which is one of various reactive vapor deposition methods. Magnetic properties, hardness and corrosion resistance of Fe-C films have been studied. It was found that single-phase Fe₃C was synthesized by electron shower method. When the peaks of Fe₃C films on X-ray diffraction pattern decreased and broadened with increasing of reactive gas flow rate, saturation magnetization (B_s) monotonously decreased. Saturation magnetization of Fe₃C was measured to be 1.2 T of which value was much higher compared with that of iron oxide. This thin film was 2times harder than that of α-Fe. In addition, the corrosion resistance was evaluated by measuring of the loss-rate of B_s in moist air of 90% R. H. at 60 °C over a period of 40 days. The loss-rate of B_s of this thin film decreased 5 % after 40 days.

View full abstract

Photoelectrochemical deposition of noble metals (Pt and Pd) was observed in the solution containing riboflavin, noble metal ion, and ethylenediaminetetraacetic acid (EDTA). From the changes in the concentration of dissolved oxygen in the solution and the amount of deposited Pt upon irradiation, the deposition mechanism of noble metals is assumed to be as follows: 1) Riboflavin absorbs light, and produces a photoexcited electron in LUMO and an electron-vacancy (hole) in HOMO, respectively. 2) Free EDTA (that was not used for forming the Pt (IV)-EDTA complex) donates an electron to the hole in HOMO. The photoexcited electron in LUMO flows to oxygen in the solution at first, and thus riboflavin is regenerated. 3) After the oxygen concentration in the solution decreases to zero, the photoexcited electron in LUMO then transfers to the Pt (IV) -EDTA complex, and reduces it to platinum metal.
Deposition of fine platinum particles onto a riboflavin-incorporated perfluorinated sulfonic a cid polymer (Nafion) membrane was accomplished upon irradiation.

View full abstract

The oxidation of phenol with hydrogen peroxide was catalyzed by the combination of H₅PMo₁₀V₂O₄₀ with Fe²⁺ in a water-chloroform-acetic acid biphase system at 55 °C, resulting in a yield of benzoquinone of 46% with 94% selectivity.

View full abstract

The reaction of guaiazulene (1) with a 0.25 molar amount of phthalaldehyde, isophthalaldehyde and terephtalaldehyde in acetic acid at room temperature (25 °C) for 4 h under argon readily gave the corresponding 3, 3'-methylenediguaiazulene having a substituent at C-α position (2, 85% yield; 3, 35%; 4, 26%; 5, 92%, respectively). The structures of these products were established on the basis of their spectroscopic (UV/VIS, IR, NMR and MS) data. A possible reaction pathway for the formation of these compounds is discussed.

View full abstract

Screening of inhibitors for ethylene formation and their use to maintain freshness of cut flowers were studied. By the addition of the analogs, such as cyclopropanol, of the intermediate of ethylene formation from 1-aminocyclopropane-1-carboxylic acid, the ethylene formation was suppressed, and the freshness of the roses was maintained.

View full abstract