Site‐Selective Iron(III) Chloride‐Catalyzed Arylation of 4‐Aryl‐4‐methoxy‐2,5‐cyclohexadienones for the Synthesis of Polyarylated Phenols

The iron(III) chloride‐catalyzed Friedel–Crafts arylation of 4‐aryl‐4‐methoxy‐2,5‐cyclohexadienones, which were easily prepared by the phenyliodine(III) diacetate (PIDA)‐mediated oxidation of 4‐arylphenols in methanol, proceeded site‐selectively to form meta‐terphenyl (2,4‐diarylphenol) derivatives in good yields. The subsequent PIDA‐mediated oxidation and iron(III) chloride‐catalyzed Friedel–Crafts arylation of the resulting products gave the corresponding 2,4,6‐triarylphenol derivatives. The present method provides useful highly substituted polyarylated compounds.

     

Accumulation of nitrous oxide in aerobic groundwaters

N₂O concentrations in the groundwaters collected in the Kanto District and Nagano Prefecture in Japan and five counties in New York State were determined. These N₂O data were obtained from the water samples from wells, springs and seepages from soils in forests and cropping fields. The N₂O concentrations in all samples greatly exceeded those of atmospheric equilibration. The average concentration of 690 nM N₂O is one order of magnitude larger than that in deep ocean. All groundwaters of the present study were aerobic with a high level of NO₃⁻, but with the absence of NO₂⁻ and NH₄⁺, and with a very low level of dissolved organic carbon. These characteristics suggest that the nitrate respiration in the aquifers is of little significance for the production of N₂O.

ΔN₂O/NO₃⁻ molar ratios in the groundwaters were between 10⁻⁴ and 10⁻² (Δ indicates the excess gas over that which would be in equilibrium). This supports the above view since the observed N₂O yield agrees with that reported for the production during an ammonia oxidation. If nitrification was indeed a major mechanism for the production of groundwater N₂O, subsequent release of N₂O from the aquifers that are polluted with nitrogen may deserve more close attention as a potential source of atmospheric N₂O via diffusion and discharge.     

Synthesis of calcium carbonate vaterite crystals and their effect on stabilization of suspension polymerization of MMA

Spherical calcium carbonate vaterite crystals were synthesized and the effect of them on stabilization of suspension polymerization of methyl methacrylate was investigated. Suspension polymerization of methyl methacrylate could be stabilized with calcium carbonate vaterite crystals and sodium dodecylbenzene sulfonate of the concentrations from 25 to 100 ppm. Poly(methyl methacrylate) beads coated with spherical calcium carbonate vaterite crystals were prepared. With an increase in the concentration of sodium dodecylbenzene sulfonate from 25 to 100 ppm, the amount of calcium carbonate vaterite crystals adhered on the surface of poly methyl methacrylate bead increased and the mean diameters of the polymer beads decreased.     

Thermal cis–trans conversion in thiophene oligomers

Thermal cis–trans conversion has been examined in oligothiophene single molecules encapsulated in the molecular vessels of cyclodextrin and Na-mordenite. At high temperatures, optical absorption intensities are enhanced in bithiophene, terthiophene and quinquethiophene, while the intensity of quarterthiophene is temperature independent. Optical absorption comes from uncompensated transition dipole moment due to the thermal torsion between cis and trans forms.     

Structural Investigation of 95(0.6Li2S0.4SiS2)5Li4SiO4 Oxysulfide Glass by Using X-ray Photoelectron Spectroscopy

S2 p and O1 s photoelectron spectra were obtained for the 95(0.6Li₂S0.4SiS₂)5Li₄SiO₄ oxysulfide glass prepared by twin-roller quenching. A four-peak deconvolution technique was used to separate the S2 p peak of the glass into the components of bridging and nonbridging sulfur atoms. As a result of the deconvolution of the S2 p peak, we found that ∼92% of the sulfur atoms were present as nonbridging atoms. The O1 s peak of the glass was separated into two components: bridging and nonbridging oxygen atoms. This separation of the O1 s peak indicated that ∼85% of the oxygen atoms were present as bridging oxygen atoms.     

Band Gap Modification of Diamond Photonic Crystals by Changing the Volume Fraction of the Dielectric Lattice

Photonic crystals with a diamond structure of epoxy lattices in which TiO₂-based ceramic particles are dispersed were fabricated by stereolithography. The periodicity of the lattice was designed to reflect electromagnetic waves in the gigahertz range. The volume fraction (β) of the dielectric lattice medium was modified from 14% to 33% by changing the rod diameter of the lattice. The photonic band gap was observed along Γ-L 〈111〉, Γ-X 〈100〉, and Γ-K 〈110〉 directions and the complete photonic band gap was formed at over β= 20%. The width of the forbidden gap increased gradually when the β increased over 14%, and reached 2.4 GHz at β= 33%. These results agreed with the band calculation using the plane wave expansion method.     

13C and Alkali NMR Studies of Electronic and Structural Properties of Alkali Fullerides

Abstract

Extensive NMR experiments have been performed both on the ¹³C and the alkali NMR in A_nC₆₀. In the superconducting A₃C₆₀. evidences for uniaxial molecular rotations of the C₆₀ and for a low T structural anomaly will be given. The linear chain structure of A₁C₆₀ is revealed by Magic Angle Spinning NMR, while its magnetic properties are studied by ¹³C and ⁸⁷Rb wideband NMR.     

Combustion Synthesis of the Titanium-Aluminum-Boron System

TiB₂ and Al base composite powders, which will offer a weight-saving improvement in stiffness, were produced by combustion synthesis of Ti, Al, and B ternary powder mixtures. Finely dispersed TiB₂ was synthesized by reacting a mixture of Ti, Al, and B in the molar ratio of 1:1:4. The grain size of the TiB₂ formed was <0.5 μm, which was much smaller than that obtained from the reaction of a mixture of Ti, Al, and B in the molar ratio 1:1:2. These results are discussed in light of the reaction propagating velocity and heat removal during the combustion synthesis process.     

Fabrication of Three-Dimensional Micro Photonic Crystals of Resin-Incorporating TiO2 Particles and their Terahertz Wave Properties

Three-dimensional (3D) photonic crystals with a diamond structure made from 40 vol% TiO₂–acrylate dielectric composites were formed by means of a CAD/CAM micro-stereolithography system. The lattice constant of the diamond unit cell was 500 μm and the forming accuracy was 10 μm. The photonic band gap in the Γ–X 〈100〉 direction measured by terahertz-time-domain spectroscopy appeared at 280–360 GHz, which agreed fairly well with the band gap calculated by the plane wave expansion method.     

Titanium aluminide coating on titanium surface using three-dimensional microwelder

Feasibility of a new method of titanium aluminide coating on titanium surface based on a reaction between aluminum liquid beads and the surface of titanium substrate has been studied using a computer-aided three-dimensional microwelder (3DMW) designed by the present authors. A predetermined length of thin aluminum wire was fed onto the substrate surface, and a spark was stricken from a thin electrode of a W-Ce₂O₃ alloy to make a small aluminum liquid bead on the substrate surface and to simultaneously melt a small area of the substrate surface beneath the bead. All conditions including the length of the wire feeding, the position of the electrode, electric power, etc. had been programmed beforehand. The liquid bead containing aluminum and titanium rapidly solidified on the titanium substrate surface producing titanium aluminides on it. Repetition of the aluminum wire feeding, the electrode positioning and the spark striking produced a coating layer consisting of sub-layers of TiAl₃, TiAl and Ti₃Al from the surface side to the substrate side. Vickers hardness and wear resistance of the coated sample were remarkably improved.