Synthesis of polyester by direct polycondensation with triphenylphosphine

Direct polycondensation reactions of various dicarboxylic acids and diols were carried out at room temperature with triphenylphosphine and polyhalo compounds to obtain polyesters in good yield. Reaction conditions including solvent, temperature, concentration of monomer, amount of reagents, and effect of matrix on direct polycondenation were investigated. A combination of triphenylphosphine and hexachloroethane was found to be satisfactory for the polyester synthesis. The addition of matrix polymers such as poly(4-vinylpyridine) in the reaction system enhanced the direct polycondensation reaction, and a polyester with a solution viscosity of 2.24 was obtained from bisphenol A and isophthalic acid under the optimum condition.     

Adsorbed state of nitrogen on ruthenium catalysts: TPD and isotopic study

The adsorbed state of nitrogen on Ru catalysts was studied by a TPD technique combined with an isotopic technique. (1) A molecular and an atomic species on Ru powder, (2) a molecular and three atomic species on Raney-Ru, and (3) two molecular and probably three atomic species on Raney-Ru/K were identified, respectively. Relations between the adsorbed states and those reactivities for an isotopic equilibration reaction of N₂ were discussed.     

Kinetics of the autoxidation of vitamin A catalysed by cobalt ion

Vitamin A,dissolved in liquid paraffin, is stable below room temperature, but suffers oxidative decomposition at 80°, giving its epoxide as the main product. The rate of decomposition of vitamin A (V_A) at 80° in the presence of oxygen (partial pressure of p) and a small amount of cobaltous stearate (Co) is expressed as: d[V_A]/dt = 3·15 × 10⁻¹:[V_A][Co] p^1·48 + 1·51 × 10⁻⁵[V_A]p^0·33 + 0·33 × 10⁻⁵[V_A], where the last term represents the spontaneous thermal decomposition.     

Chiral sulfoxides as neutral coordinate-organocatalysts in asymmetric allylation of N-acylhydrazones using allyltrichlorosilanes

Sulfoxides were first introduced to the allylation of N-acylhydrazones with allyltrichlorosilanes as effective neutral coordinate-organocatalysts (NCOs). Both high diastereo- and enantioselectivity were attained when optically active chiral sulfoxides were used. Asymmetric crotylations using (Z)- and (E)-crotyltrichlorosilanes showed a high level of stereospecificity (Z --> anti and E --> syn) with high enantioselectivity.     

Aggregation behavior of polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer in N‐methylpyrrolidone

Solution property of hydrogenated polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer (SEBS copolymer) was studied by using static light scattering and dynamic light scattering for cyclohexane and N‐methylpyrrolidone (NMP) solutions. From the values of dimensionless parameters ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, and solubility parameters, SEBS copolymer proved to exist as single chain close to random coil in nonpolar cyclohexane, whereas aggregate into the core‐shell micelle consisting of poly(ethylene/butylene) (PEB) core surrounded by PS shell in polar NMP. The core‐shell micelle formed in NMP is composed of 65 polymer chains, having three times larger average chain density (d = 0.12 g cm^?3) than a single polymer chain (d = 0.04 g cm^?3) in cyclohexane. The comparison with the aggregation behaviors in other solvents demonstrated that the aggregate compactness of the copolymer depended largely on solvent polarity, resulting in formation of the highly dense PEB core (R_c = 4.5 nm) and the thick PS shell (ΔR = 22.9 nm) in high‐polar NMP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 588–594, 2010     

Structure and intramolecular flexibility of beta-cyclodextrin complex with (-)-epigallocatechin gallate in aqueous solvent

The probable structure of the inclusion complex of beta-cyclodextrin (beta-CD) and (-)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. EGCg formed a 1:1 complex with beta-CD, in which the A ring and a portion of the C ring of EGCg were included at the head of the phenolic hydroxyl group attached to C7 of EGCg in the beta-CD cavity from the wide secondary hydroxyl group side. In the 1:1 complex with beta-CD, EGCg maintained the conformation in which the B and B' rings of EGCg took pseudoequatorial and pseudoaxial positions with respect to the C ring, respectively. The structure of the inclusion complexes of beta-CD and EGCg obtained from NMR experiments supported those determined from AM1 semiempirical SCF MO calculations well.     

Aqueous chromatography system using pH- and temperature-responsive stationary phase with ion-exchange groups

We report on the development of a novel analytical HPLC technique of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, ketoprofen and naproxen, with an isocratic aqueous mobile phase. In this study, we designed a new pH- and temperature-responsive copolymer of N-isopropylacrylamide (NIPAAm), butyl methacrylate (BMA) and N,N-dimethylaminopropylacrylamide (DMAPAAm). The copolymer was modified with cross-linked poly(NIPAAm-co-BMA-co-DMAPAAm) (IBD) hydrogel on to aminopropyl silica beads, and the products were evaluated as HPLC packing materials for an ion-exchange- and temperature-responsive chromatography. The property of the surface of the stationary phase was altered from hydrophilic to hydrophobic, and from charged to non-charged by changes in the temperature and pH. In addition, it is possible that ion-exchange groups can appear or be hidden on the polymer chain surface by temperature changes. The interactions of NSAIDs with this stationary phase were controlled by the temperature and the pH with a constant aqueous mobile phase. PH- and temperature-responsive chromatography is expected to be useful for the separation of pharmaceuticals and biomolecules.     

Improved 2-nitrobenzenesulfenyl method: optimization of the protocol and improved enrichment for labeled peptides

We have developed the NBS (2-nitrobenzenesulfenyl) method, a quantitative proteome analysis method utilizing stable isotope labeling followed by mass spectrometry. The potential of this method was reported previously, and the procedure has now been further optimized. Here, we describe a procedure utilizing urea or guanidine hydrochloride as a protein denaturant, in conjunction with an improved chromatographic enrichment method for the NBS-labeled peptides using a phenyl resin column. By using this new protocol, both sample loss throughout the protocol and the elution of unwanted unlabeled peptides can be minimized, improving the efficiency of the analysis significantly.     

Precise determination of dissolved silica in seawater by ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry

Ion exclusion chromatograph (IEC) isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP–MS) (IEC–ID–ICP–MS) was developed for measurement of dissolved silica in seawater, which was applied to production of certified reference materials (CRMs) of three concentration levels of nutrients (high, medium and low levels). IEC–ICP–MS has been employed to separate dissolved silica from seawater matrix. In the present study, in order to solve substantial problems due to spectral interference in ICP–MS and to improve the accuracy of IEC–ICP–MS beyond standard addition or conventional calibration methods, ID method was coupled with ICP-sector field mass spectrometry (operated under medium resolution,i.e., m/Δm = 4000). In addition, effects of various operating parameters in ICP–MS on a silicon background level were also investigated to obtain lower background equivalent concentration (BEC). As a result, 3 ng g⁻¹ of the BEC and 0.5 % of relative standard uncertainties were achieved in the analyses of dissolved silica in seawater samples at concentration levels from 4.0 mg kg ^-1 to 0.8 mg kg⁻¹ as silicon. The developed method was successfully validated by analyses of an artificial seawater containing a known amount of silicate and the seawater certified reference material MOOS-2 produced by the National Research Council Canada.