Kazuaki Isomura

Decomposition of humic acid and reduction of trihalomethane formation potential in water by ozone with u.v. irradiation

Abstract Humic acids dissolved in water are decomposed by ozone under u.v. irradiation at pH 6.9. The decomposition rate of the total organic carbon (TOC) is obtained as functions of the u.v. intensity and the residual ozone concentration, assuming the reaction obeys first order kinetics with respect to reactive TOC concentration. Major final products are acetic acid, formic acid and oxalic acid, which are refractory to ozonation and are no longer precursors of trihalomethanes. The amount of chloroform and total organic chlorides generated by chlorination are drastically decreased by u.v. irradiation. No increase in the trihalomethane formation potential is observed in the course of u.v. ozonation.

Noncentrosymmetric Langmuir-Blodgett Film of Phenylpyrazine Derivative Applicable to Nonlinear Waveguides

Thick noncentrosymmetric LB films of more than 200 bilayers (thickness of more than 1 µm) were successfully fabricated with an alternating deposition of a phenylpyrazine derivative and arachidic acid monolayers. The alternating LB films were transparent from visible to near infrared region. Spectroscopic and X-ray diffraction studies on the alternating LB films proved that molecules were predominantly oriented normal to the film plane in the LB film. Further, the quadratic dependence of second-harmonic (SH) intensity on film thickness was confirmed in the LB films in the wide range of thickness from 1 to 200 bilayers. From the SH generation measurement, the alternating LB films were found to have fairly large second-order nonlinear susceptibility, which was estimated to be 1×10-7 esu.

Destruction rate of volatile organochlorine compounds in water by ozonation with ultraviolet radiation

Abstract Rates of ozonation of 1,1,1-trichloroethane, trichloroethylene and tetrachloroethylene were measured in a rectangular thin channel reactor with a continuous flow of reactants under u.v. irradiation. These substances were chosen as model compounds of pollutants in groundwaters. The solution was buffered with KH 2 PO 4 -Na 2 HPO 4 at pH = 6.9. The destruction rates were proportional to the dissolved ozone concentration and the u.v. intensity in the reactor. The u.v. irradiation of 8 W m −2 at 253.7 nm enhanced the destruction rate of the organochlorine compounds by more than ten times that of the ozonation without u.v. irradiation. The activation energy for the decomposition of 1,1,1-trichloroethane decreased with increasing u.v. intensity. No volatile organochlorine compounds were newly formed in these reactions.

Electronic structures of vinylazide, vinylnitrene and 2H-azirine. Mechanism of the reaction from vinylazide to 2H-azirine

Abstract The mechanism of the conversion of vinylazides into 2H-azirines is examined by use of ab initio MO calculations. It is ascertained that vinylnitrenes have very weak bonds between the vinylazides and nitrogen molecule parts. It seems to decompose readily into the two fragments. This is one of the most characteristic features of vinylazides. The reaction is shown to proceed with N2 at the tail of the vinylnitrene part. This mechanism accounts well for experimental results of the reaction.

Pyroelectricity of Noncentrosymmetric Langmuir-Blodgett Films of Phenylpyrazine Derivatives

Pyroelectricity of alternating Langmuir-Blodgett (LB) films consisting of phenylpyrazine derivatives and stearic acid was measured by the static method at various temperatures. It was found that the LB films consisting of a compound with highly conjugated π-electron system showed large pyroelectricity which was greatly dependent on the temperature of the sample films. The sign of the pyroelectric coefficients changed at a temperature characteristic of the films. In the high-temperature range, a dull pyroelectric response was observed. The pyroelectricity of LB films with various ion complexes was also examined. The films of polyion complex which had more spatial freedom showed larger pyroelectricity. However, an extremely sparse molecular packing gave a low degree of molecular orientation in the film resulting in small pyroelectricity.

Second-order nonlinear optical Langmuir-Blodgett films of pyrazine derivatives

Using two new pyrazine derivatives, we could obtain thick noncentrosymmetric Langmuir-Blodgett (LB) films with more than 50 pyrazine layers. In the pyrazine LB films, the second-harmonic intensity was quadratically increasing with the number of deposited pyrazine layers. From the second-harmonic generation measurement, the pyrazine LB films were demonstrated to have fairly large second-order susceptibility.

Fourier transform-infrared spectra and molecular orientation in thin Langmuir—Blodgett films of dodecyloxyphenylpyrazine carboxylic acid and its barium salt

Abstract Fourier transform-infrared transmission and reflection—absorption (RA) spectra have been measured for Langmuir—Blodgett (LB) films, 1 to 11 monolayers thick, of 5-( p -dodecyloxyphenyl) pyrazine-2-carboxylic acid (DOPC) and its barium salt. Spectral changes occur in DOPC with reduction in temperature, suggesting the coexistence of the cis and trans isomers for the N(1)C(2) bond in the pyrazine ring and the CO bond of the carboxyl group. The enthalpy difference between the two isomers was calculated as 160 cal mol −1 . By comparing the intensities of major absorption bands in the transmission and RA spectra, orientation angles of the transition moments were evaluated. The molecular orientation of DOPC in the LB films was found to be independent of the number of monolayers, and also unaltered by conversion to the barium salt. This suggests that the molecular orientation is mainly governed by and intermolecular interaction between the adjacent phenyl-pyrazine chromophores.

New thermal rearrangement of 2H-azirines: Formation of enamines and their cyclization into pyridines

Abstract Intermediary formation of enamines in the course of cyclization of vinyl nitrenes into 6-membered ring compounds showed that this reaction proceeded not by insertion but by consecutive hydrogen shift and electrocyclic reaction.

Scanning tunneling microscope observation of a polar liquid crystal and its computer simulation

The scanning tunneling microscope (STM) constructed in the laboratory was utilized to observe the molecular arrangement of a new type of liquid crystalline molecule, 5-(p-dodecyloxyphenyl)pyrazine-2-carbonitrile (DOPPC), which has large dipole moments along the molecular axis. The DOPPC molecules adsorbed on a graphite substrate showed several different STM images with regular two-dimensional molecular arrays. They revealed a novel interdigitated double-row structure, differing from the single-row and the double-row structures proposed for the STM images of cyanobiphenyl liquid crystals. Moreover, a computer calculation was conducted based on electrostatic multipole-multipole interaction and simulated the most energetically preferable molecular arrangement, which agreed well with the observed STM image.

Theoretical study on the effect of heterocycles reinforcing the layered structure

In order to elucidate the origin of different behaviors of amphiphiles at the air-water interface depending on the heterocycle incorporated, intralayer multipole-multipole electrostatic energy in a two-dimensional crystalline arrangement was calculated, simulating a monolayer. The calculated interaction energies well explain the actual behavior which shows the validity of this method in the molecular design of amphiphiles.