Temperature gradient interaction chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of air terminated polystyryllithium

The reaction products of polystyryllithium with air were characterized by size-exclusion chromatography, temperature gradient interaction chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Polystyryllithium was prepared by anionic polymerization of styrene initiated with sec-butyllithium in cyclohexane under an Ar atmosphere. It was confirmed that polystyryl ketone, polystyryl alcohol, and directly coupled polystyrene were the major products in addition to the normally terminated polystyrene, which is consistent with the results in the literature. We could also identify the presence of methoxy and carboxylic acid end capped polystyrenes as well as dipolystyryl ether as minor products. Among the minor products, dipolystyryl ether has not been reported yet.     

Decomposition of Cyanogen Chloride by Using a Packed Bed Plasma Reactor at Dry and Wet Air in Atmospheric Pressure

The decomposition rate of CNCl in a BaTiO₃-filled Packed Bed Plasma Reactor was studied as a function of AC input power, power frequency, residence time in the reactor, and inlet flow rate. The decomposition rate was compared with those of CH₃CN and CCl₂CHCl. Under the condition of 6.7 Wh/m³ specific energy den- sity, the decomposition rate of CNCl was found to be 50%, which is lower than those of CH₃CN and CCl₂CHCl at the same or similar conditions. At a higher frequency of the power input system, the decomposition rate of inlet gas becomes lower due to a decrease in field strength for the same level of power. And, under the same level of input power, a higher decomposition rate was obtained at an increased residence time. The relation between gas decomposition rates stemmed from the electron–molecule collision and bounding energy within the molecule. The decomposition ratio of CNCl was lower than those of CCl₂CHCl and CH₃CN because the bond strength of the weakest bond in the molecule is higher. In order to test the decomposition efficiency of CNCl with catalytic packing material in a plasma reactor, the catalyst of γ-Al₂O₃ and Pt/γ-Al₂O₃ was packed in the packed bed plasma reactor. Although byproducts were formed, the plasma-catalyst hybrid reactor containing Pt/γ-Al₂O₃ showed a higher efficiency in CNCl decomposition as shown in the decomposition rate of above 99% in 0.3 kWh/m³.     

Organization of branched rod-coil molecules into a 3-D tetragonally perforated lamellar mesophase

Tetramerization of coil-rod-coil ABC triblock copolymers to a tetrabranched molecule induces an unusual 3-D tetragonally perforated layered liquid crystalline phase as an intermediate structure between 1-D lamellar and 2-D hexagonal columnar phases.     

Effect of acidic treatment on metal adsorptions of pitch-based activated carbon fibers

In this work, the pitch-based activated carbon fibers (ACFs) were prepared by nitric acid to investigate the multi-metal adsorption in interfacial and textural points of view. N2/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were studied by BET specific surface area and t-plot methods, respectively. As a result, the specific surface area of the almost neutral ACFs in nature significantly decreased with nitric acid treatment, probably due to the widening of micropores. However the total acidity, including the carboxyl groups, on carbon surfaces was extremely induced during the acidic surface treatment. From the adsorptions of Cu2+ and Ni2+, it was revealed that the adsorption capacity of metal ions was mainly influenced by the weakly acidic functional groups such as lactones on the carbon surfaces at pH < pI (isoelectric point), and by the strongly acidic functional groups such as carboxyl groups at pH > pI.     

Determination of mono- to octachlorobiphenyls in fish oil using florisil adsorption followed by headspace solid-phase microextraction and gas chromatography with time-of-flight mass spectrometric detection

A simple and reliable method for the determination of polychlorinated biphenyls (PCBs) from mono- to octachlorobiphenyls in fish oil for dietary supplement is described. The method combines Florisil clean up and headspace solid-phase microextraction on 65 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB). Analyte detection was carried out using GC-time-of-flight mass spectrometry (GC-TOF-MS). Fifty three PCB congeners including the seven indicator PCBs (IUPAC Nos. 28, 52, 101, 118, 138, 153 and 180) were analyzed. Under optimal conditions, the method detection limit (MDL) of each congener in the range from 0.8 to 31 ng/g was found. A certified reference material (BCR-349) was analyzed and it showed good agreement with the certified data.     

Studies on the alkylation of phenolate in an organofluorine solvent and its application to the synthesis of myrsinoic acids A and E

Among the distinct features of organofluorines, solubility properties to molecules often enable unique applications. More importantly, organofluorines can be compatible with chemical reactions in general, even under harsh conditions. In this context, a study on the alkylation of phenolate using an organofluorine solvent were performed for the preparation of ortho-alkyl phenols. Herewith, the study on the alkylation of phenolate in an organofluorine solvent as well as its application to the synthesis of bioactive terpenylated phenolic natural products, myrsinoic acids A and E, will be reported. Our study suggested that organofluorine solvents could be better alternatives to the conventional nondissociating solvents as organic reaction media to suppress the nondesirable and nonselective side reactions such as in the ortho-alkylation of phenolate.     

A Study on the Ring Transformation of Dihydroisoxazolopyrimidine

Dihydroisoxazolopyrimidine derivatives could be cleaved to form either pyrimidine ring or isoxazole ring derivatives depending upon the reaction conditions employed.     

A Convenient Synthesis of Nitrile Oxides from Aldoximes by 1-Chlorobenzotriazole

Nitrite oxides can be conveniently prepared from aldoximes utilizing 1-chlorobenzotriazole in dichloromethane. The reaction and work-up procedures are simple and the isolated yields high.     

Regioselectivity and Stereoselectivity in the Intramolecular Nitrile Oxide-Olefin Cycloaddition (INOC) Reaction and the Intramolecular Silyl Nitronate-Olefin Cycloaddition (ISOC) Reaction

Both INOC and ISOC reactions of 1 which has two different double bonds in a molecule (allylic and homoallylic double bond) showed high regioselectivity for allylic double bond to make [5,5] ring system. INOC reactions of 1 and 6 showed high diastereoselectivity for 4-substituents, whereas ISOC reaction did for 6-substituents of tetrahydrofuroisoxazolines.     

Structural transitions of nanocrystalline domains in regioregular poly(3‐hexyl thiophene) thin films

The effects of solution processing and thermal annealing on thin film morphology and crystalline structures of regioregular poly(3‐hexyl thiophene) (RR P3HT) are studied in terms of molecular weight (M_w). Using grazing‐incidence X‐ray diffraction, π‐conjugated planes in drop‐cast films from chloroform solutions are found to be preferentially oriented parallel to the substrates regardless of M_w. However, the mesoscale nanocrystalline morphology of the drop‐cast films is significantly affected by M_w, exhibiting a distinctive morphological transition from short nanorods to long nanofibrils above a critical number‐averaged M_w (～ 3.6 kDa). This is probably due to the change in a conformation change from an extended‐chain to a folded‐chain, as M_w of RR P3HT increases. In contrast, spin‐casting of high M_w RR P3HT produces less ordered films with a lower crystallinity and mixed parallel/perpendicular orientations of π‐conjugated planes. The crystallinity and parallel π‐conjugated orientation of RR P3HT in spin‐cast films could be improved by thermal treatments at high‐temperatures either (1) above the glass transition temperature or (2) above the melting temperature of RR 3PHT followed by recrystallization upon cooling under vacuum. However, the charge mobility of the spin‐cast films for a field‐effect transistor application is still lower than that of the drop‐cast films. This would be attributed to the chain oxidation and the development of distinct grain boundaries between RR P3HT nanofibrils during the thermal treatments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1303–1312, 2007