Investigations on poly(vinyl chloride). I. Evolution of aromatics on pyrolysis of poly(vinyl chloride) and its mechanism

Poly(vinyl chloride) (PVC) alone or mixed with 10 wt-% and 50 wt-% TiO₂, SnO₂, ZnO, and Al₂O₃ were pyrolyzed by using a pyrolysis gas chromatograph. Benzene, toluene, ethylbenzene, o-xylene, styrene, naphthalene, and various chlorobenzenes were identified. No hydrocarbons could be detected in pyrolysis products of any samples at 200°C. More aromatic hydrocarbons than aliphatic hydrocarbons are released from the PVC–TiO₂ system and in preheated PVC. The contrary result is observed in the PVC–ZnO and PVC–SnO₂ systems. Aromatics having methyl endgroups are easily released from the PVC–ZnO and PVC–SnO₂ systems and at elevated pyrolysis temperature, because methylene groups are easily isolated along the chain by ZnO, SnO₂ and the heating. The release of ethylbenzene o-xylene, and chlorobenzenes suggests a repeated dehydrochlorination and recombination of HCl and Cl₂ to double bonds along the chain. Possible decomposition mechanisms of PVC are discussed.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-furancarbothiohydrazone

2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 10⁴ liters mole^?1 cm^?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pK_a1 = 2.88 and pK_a1 = 6.70 at 25 °C and μ = 0.1.     

Fast separation of oligonucleotide and triplet repeat DNA on a microfabricated capillary electrophoresis device and capillary electrophoresis

A laser-induced fluorescence detection system coupled with a highly sensitive silicon-intensified target (SIT) camera is successfully applied to the imaging of a band for DNA fragment labeling by fluorescence dye in a microchannel, and to the visualizing of the separation process on a microfabricated chip. We demonstrated that an only 6 mm separation channel is sufficient for the separation of triplet repeat DNA fragment and DNA molecular marker within only 12 s. The separation using the microfabricated capillary electrophoresis device is confirmed to be at least 18 times faster than the same separation carried out by conventional capillary electrophoresis with 24.5 cm effective length. The use of a short capillary with 8.5 cm effective length is also efficient for fast separation of DNA; however, the microchip technology is even faster than capillary electrophoresis using a short capillary.     

NMR, UV-vis and CD study on the interaction of pradimicin BMY-28864 with divalent cations of alkaline earth metal

In order to clarify the mechanism of the calcium-activated anti-fungal action of pradimicin derivatives, we investigated the compatibility of four divalent metal cations, Ca2+, Mg2+, Sr2+ and Ba2+, when combined with pradimicin BMY-28864 in an aqueous solution. The 1H NMR studies suggest that all the tested cations can induce a chemical exchange between two types of aggregation of BMY-28864 in an aqueous solution. The exchange rate, however, varies according to the cation species. In descending order they are: Ba2+ > Sr2+ > Ca2+ > Mg2+. The differences in the binding ability of BMY-28864 to the cations and the solubility of the chloride salts are explained by the electronegativity of these cations. The UV-Vis and CD spectra of these solutions show isosbestic points that correspond to an exchange process in the cations' binding to BMY-28864. The results provide experimental support for the hypothesis that there is a common mechanism underlying their cations interactions with the antibiotic. The CD study also provided evidence about the stoichiometric relation of the divalent metal ions to the antibiotic, 1:2, which was obtained by NMR analyses.     

Kinetic study of the electron-transfer oxidation of the phenolate anion of a vitamin E model by molecular oxygen generating superoxide anion in an aprotic medium

Electron-transfer reduction of molecular oxygen (O2) by the phenolate anion (1-) of a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), occurred to produce superoxide anion, which could be directly detected by a low-temperature EPR measurement. The rate of electron transfer from 1- to O2 was relatively slow, since this process is energetically unfavourable. The one-electron oxidation potential of 1- determined by cyclic voltammetric measurements is sufficiently negative to reduce 2,2-bis(4-tert-octylphenyl)-1-picrylhydrazyl radical (DOPPH*) to the corresponding one-electron reduced anion, DOPPH-, suggesting that 1- can also act as an efficient radical scavenger.     

Monolithic silica columns with various skeleton sizes and through-pore sizes for capillary liquid chromatography

Reduction of through-pore size and skeleton size of a monolithic silica column was attempted to provide high separation efficiency in a short time. Monolithic silica columns were prepared to have various sizes of skeletons (approximately 1-2 microm) and through-pores (approximately 2-8 microm) in a fused-silica capillary (50-200 microm I.D.). The columns were evaluated in HPLC after derivatization to C18 phase. It was possible to prepare monolithic silica structures in capillaries of up to 200 microm I.D. from a mixture of tetramethoxysilane and methyltrimethoxysilane. As expected, a monolithic silica column with smaller domain size showed higher column efficiency and higher pressure drop. High external porosity (> 80%) and large through-pores resulted in high permeability (K = 8 x 10(-14) -1.3 x 10(-12) m2) that was 2-30 times higher than that of a column packed with 5-mirom silica particles. The monolithic silica columns prepared in capillaries produced a plate height of about 8-12 microm with an 80% aqueous acetonitrile mobile phase at a linear velocity of 1 mm/s. Separation impedance, E, was found to be as low as 100 under optimum conditions, a value about an order of magnitude lower than reported for conventional columns packed with 5-microm particles. Although a column with smaller domain size generally resulted in higher separation impedance and the lower total performance, the monolithic silica columns showed performance beyond the limit of conventional particle-packed columns under pressure-driven conditions.     

WKB-like wave-functional for a string state and path-dependent phase factor

The variational calculation of the path-ordered phase factor is streamlined. We propose that the wave functional for a string state is approximately of the form

$\text{Ψ[x(σ)=}\text{Π}\text{σ′}\text{K(x(σ′))}\text{P exp}\text{ie∫}\text{A d}\text{x}$

.The real factor K is shown to be proportional to the square root of the dielectric permeability in the Kogut-Susskind-'t Hooft model of colour flux collimation.     

Double Pore Silica Gel Monolith Applied to Liquid Chromatography

Silica gels retaining double pore structure in the size ranges of micrometer and nanometer have been applied to the rod-shaped monolithic column for liquid chromatography. The macropore structure was designed by controlling the phase separation process induced by the hydrolysis and polycondensation of alkoxysilane, whereas the mesopore structure was tailored by the solvent exchange treatments on wet gels. The size exclusion chromatograms on polystyrene standards exhibited almost similar features for octadecyl-modified rod and conventional packed beads columns. The dependence of plate height on the velocity of mobile phase determined for amylbenzene was by far weaker in the rod column than in the packed beads column, suggesting that additional geometrical factors should be considered in describing the separation mechanism in the rod column.     

Synthesis of 1,8- and 2,8-dihydrocycloheptapyrazol-8-one derivatives by the reactions of 3-acetyltropolone and its methyl ethers with phenylhydrazine

3-Acetyltropolone ( 1 ) reacted with phenylhydrazine to give 3-acetyltropolone phenylhydrazone ( 3 ) and 3-methyl-1-phenyl-1,8-dihydrocycloheptapyrazol-8-one ( 4 ). The former ( 3 ) cyclized to afford the latter ( 4 ). The reaction of 3-acetyl-2-methoxytropone ( 2a ) with phenylhydrazine gave 4 , 3-methyl-2-phenyl-2,8-dihydrocyclo-heptapyrazol-8-one ( 5 ), and 3-methyl-2-phenyl-2,8-dihydrocycloheptapyrazol-8-one phenylhydrazone ( 6 ). The compound ( 5 ) reacted with phenylhydrazine to afford 6 . The reaction of 7-acetyl-2-methoxytropone ( 2b ) with phenylhydrazone gave 7-acetyl-2-methoxytropone phenylhydrazone ( 7 ), 7-acetyl-2-(N′-phenylhydrazino)-tropone phenylhydrazone ( 8 ), 3-methyl-1-phenyl-1,8-dihydrocycloheptapyrazol-8-one phenylhydrazone ( 9 ), and 6 . The compound ( 7 ) was heated to afford 4 and reacted with phenylhydrazine to afford 8 and 9 . The compound ( 8 ) was also refluxed to give 9 .