Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

Summary The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. R_F values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm^–3 and 0.01–3 mol dm^–3, respectively, and are compared with those obtained with Avicel SF. R_F spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme R_F values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.     

Rapid PCR in a continuous flow device

Continuous flow polymerase chain reaction (CFPCR) devices are compact reactors suitable for microfabrication and the rapid amplification of target DNAs. For a given reactor design, the amplification time can be reduced simply by increasing the flow velocity through the isothermal zones of the device; for flow velocities near the design value, the PCR cocktail reaches thermal equilibrium at each zone quickly, so that near ideal temperature profiles can be obtained. However, at high flow velocities there are penalties of an increased pressure drop and a reduced residence time in each temperature zone for the DNA/reagent mixture, that potentially affect amplification efficiency. This study was carried out to evaluate the thermal and biochemical effects of high flow velocities in a spiral, 20 cycle CFPCR device. Finite element analysis (FEA) was used to determine the steady-state temperature distribution along the micro-channel and the temperature of the DNA/reagent mixture in each temperature zone as a function of linear velocity. The critical transition was between the denaturation (95 degrees C) and renaturation (55 degrees C-68 degrees C) zones; above 6 mm s(-1) the fluid in a passively-cooled channel could not be reduced to the desired temperature and the duration of the temperature transition between zones increased with increased velocity. The amplification performance of the CFPCR as a function of linear velocity was assessed using 500 and 997 base pair (bp) fragments from lambda-DNA. Amplifications at velocities ranging from 1 mm s(-1) to 20 mm s(-1) were investigated. The 500 bp fragment could be observed in a total reaction time of 1.7 min (5.2 s cycle(-1)) and the 997 bp fragment could be detected in 3.2 min (9.7 s cycle(-1)). The longer amplification time required for detection of the 997 bp fragment was due to the device being operated at its enzyme kinetic limit (i.e., Taq polymerase deoxynucleotide incorporation rate).     

Hydrogenation of benzaldehyde and cinnamaldehyde in compressed CO2 medium with a Pt/C catalyst: a study on molecular interactions and pressure effects

The hydrogenation of benzaldehyde and cinnamaldehyde has been studied with a 5% Pt/C catalyst in compressed CO(2). The effect of CO(2) pressure on the total conversion was found to be different between the two aldehydes. The total conversion of benzaldehyde merely decreases with increasing CO(2) pressure, while that of cinnamaldehyde shows a maximum at a certain pressure. High-pressure FTIR measurements indicate the existence of interactions of CO(2) with the aldehydes. The absorption of nu(C=O) red-shifts at increasing CO(2) pressure, and this red-shift is more significant for cinnamaldehyde than for benzaldehyde, indicating that the C=O bond of the former becomes more reactive than the latter. The difference in the mode of interactions of CO(2) with these aldehydes has also been indicated by changes of nu(C=O) of CO(2). Thus, the conversion of benzaldehyde will decrease with increasing CO(2) pressure because of a simple dilution by introducing a larger quantity of CO(2). For cinnamaldehyde, the conversion will increase at low pressures because of increasing interactions with CO(2) molecules (increasing the reactivity of the C=O bond) but decrease at high pressures because of the simple dilution effect, similar to the case of benzaldehyde. The dense CO(2) molecules are not likely to change the catalytic activity of supported Pt particles, which was previously suggested from optical absorption of supported fine metal (Au) particles in a compressed CO(2) medium.     

Characterization and quantitation of clarithromycin polymorphs by powder X-ray diffractometry and solid-state NMR spectroscopy

Characterization of clarithromycin polymorph was performed by solid-state cross polarization and magic angle spinning (CP/MAS) 13C-NMR spectroscopy. Two polymorphs, form II and form I, of clarithromycins indicated characteristic resonances of C1 carbonyl carbon at 176.2 and 175.2 ppm, respectively. Since each peak of C1 carbon was well separated in the spectrum of the two polymorphs, we performed quantitative analysis of the polymorphic fraction from the peak area of these peaks. The peak area of form I was found to linearly increase with an increase of its content, with a correlation coefficient of above 0.99. Solid-state NMR was found to be a useful technique to determine the characteristics of the polymorphic forms.     

Novel Knöevenagel-type reaction via titanium enolate derived from Ti(O-i-Pr)4 and diketene

Knöevenagel-type reaction between diketene and aldehydes proceeded in the presence of Ti(O-i-Pr)₄. This reaction proceeded via titanium enolate derived from Ti(O-i-Pr)₄ and diketene. As for the stereoselectivity of the products, E-isomers were produced predominantly in the case of aromatic aldehydes.     

Intramolecularly hydrogen-bonded 3-phenacyl-lH-pyrido[3,4-b]-pyrazin-2-one and 2-Phenacyl-4H-pyrido[3,4-b]pyrazin-3-one

Twelve phenacyl derivatives of 1H-pyrido[3,4-b]pyrazin-2-ones and 4H-pyrido[3,4-b]pyrazin-3-ones have been synthesized. In these compounds, C = N double bonds at the 3 and 4 positions in the former compounds and those at the 1 and 2 positions in the latter compounds migrate onto the side chains to form phenacyli-dene structures. These migrations are facilitated by chelation between side chain carbonyl and the proton attached to the ring nitrogen atom which was generated by the migration. All the hydrogen-bonded structures appear to be stable as shown by their ir spectra in the crystalline state, and by their ¹H nmr spectra in solution.     

Synthesis and properties of new polyesters having tetrahydrofuran rings in their main chains

New polyesters 6a–6c consisting of 2,4-linked tetrahydrofuran rings were synthesized by bulk polycondensation of methyl trans- and cis-4-hydroxytetrahydrofuran-2-carboxylates ( 5a and 5b ) and a stereoisomeric mixture of methyl 4-hydroxy-5-methyltetrahydrofuran-2-carboxylate ( 5c ) at high temperature. These monomers were prepared from methyl glycolate or methyl lactate and diethyl maleate through a four-step reaction sequence. The polycondensation was carried out without solvent at different temperatures ranging from 150 to 220°C. Titanium isopropoxide was most effective among the catalysts examined, giving polyesters with number-average molecular weights up to 2 × 10⁴. Polyester 6a consisting of trans-2,4-linked tetrahydrofuran rings was soluble in trifluoroacetic acid and a mixed solvent of chloroform and methanol (10/1, v/v). Polyester 6b composed of cis-2,4-linked tetrahydrofuran rings was soluble in dimethyl sulfoxide and dimethylformamide in addition to the two solvents for 6a . Polyester 6c with 5-methyl-substituted tetrahydrofuran rings was composed of a mixture of stereoisomeric units and thus was soluble in a variety of solvents including chloroform, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and dimethylformamide. The glass transition temperatures of 6a, 6b , and 6c determined by DSC were 109, 88, and 66°C. These polyesters were found to be very slowly hydrolyzed in a neutral phosphate buffer solution at ambient temperature. © 1993 John Wiley & Sons, Inc.     

Distribution and behavior of long-lived radioiodine in soil

The concentration of¹²⁹I in soil in Japan was determined by neutron activation analysis. For the activation analysis, pre-irradiation chemical separation of the iodine was carried out by acid decomposition and distillation and post-irradiation treatment was performed by ion exchange and solvent extraction. The concentration of stable iodine and¹³⁷Cs were also determined and compared with the behavior of¹²⁹I in soil.Soil samples from Ibaraki, Fukui, Fukushima, and Nagasaki Prefectures were analyzed and¹²⁹I was detected in amounts ranging from 10^–7 to 10^–5 Bq/g soil in uncultivated surface soil. There are apparently small variations in the¹²⁹I concentrations in each of the regions analyzed.From depth profile studies in sandy soil, the iodide form of¹²⁹I was found to migrate downward at a relatively rapid rate while other species remain longer in the surface soil.     

γ-irradiation of polypropylene in vacuum and in air

Polypropylene films were irradiated with ⁶⁰Co γ-rays in vacuum or in air and stored in air. Just after irradiation, the concentration of carbonyl group of the sample irradiated in air only increased with dose. The concentrations of both samples increased with storage time. The more the absorbed doses, the higher the increasing rates. The increasing rate of the concentration of carbonyl group during irradiation in air was higher than those during storage in air. Just after irradiation, the tensile strengths and the elongations of the both samples somewhat increased with dose at the doses less than 5 Mrad, but decreased at doses more than 13 Mrad. The tensile strength and the elongation of the sample irradiated in air decreased with storage time. Those of the sample irradiated in vacuum also decreased with storage time but the decreasing rates were much smaller than those in the sample irradiated in air. The gel fractions of the samples irradiated in vacuum and annealed in vacuum were somewhat higher than those irradiated in vacuum and not annealed. To elucidate high oxidation rate in the sample irradiated in air during and after irradiation, reaction mechanisms were discussed. To clarify the difference of mechanical properties between the samples irradiated in vacuum and in air, the effect of crosslink was considered, together with the oxidation.     

Amphiphilic block copolymers of vinyl ethers by living cationic polymerization. II. Synthesis and surface activity of macromolecular amphiphiles with pendant amino groups

Amphiphilic block polymers of vinyl ethers (VEs). $\rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OCH}_{\rm 2} {\rm CH}_{\rm 2} {\rm NH}_{\rm 2} } \right)\rlap{--} ]_m \rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OR}} \right)\rlap{--} ]_n \left( {{\rm R: }n{\rm - C}_{{\rm 16}} {\rm H}_{{\rm 33}} ,{\rm }n{\rm - C}_{\rm 4} {\rm H}_{\rm 9} ;m \simeq 40,{\rm n} = 1 - 10} \right)$ were prepared, each of which consists of a hydrophilic segment with pendant primary amino groups and a hydrophobic poly(alkyl VE) segment. Their precursors were obtained by the HI/I₂-initiated sequential living cationic polymerization of an alkyl VE and a VE with a phthalimide pendant (CH₂ = CHOCH₂CH₂Im; Im; phthalimide group), where the segment molecular weights and compositions (m/n ratio) could be controlled by regulating the feed ratio of two monomers and the concentration of hydrogen iodide. Hydrazinolysis of the imide functions gave the target polymers which were readily soluble in water under neutral conditions at room temperature. These amphiphilic block polymers lowered the surface tension of their aqueous solutions (0.1 wt%, 25°C) to a minimum ? 30 dyn/cm when the hydrophobic pendant R was n-C₄H₉ (n = 4–9). The polymers with n-C₄H₉ pendants in the hydrophobic segment exhibited a higher surface activity than those with n-C₁₆ H₃₃ pendants. The surface activity of the polymers also depended on the pH of the polymer solutions; the surface activity increased in more basic solutions where the ionization of the amino group (? NH₂)2? NH₃^⊕) is suppressed.