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71.
Noritaka Ohtani Makoto Nakaya Kenji Shirahata Tsuyoshi Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2677-2686
Polystyrene-based crosslinked cationic ionomers containing ammonium or phosphonium chlorides (AxRCI and PxBuCI) were reacted with decyl methanesulfonate. The kinetic data were correlated with the swelling behavior of the ionomers and the solution viscosity of the corresponding linear ionomers. The reactivity of the ionomers was independent of the particle size of the ionomer beads, indicating no diffusion control of the reaction. The solvent and the ion content of the ionomers greatly affect the reactivity. In nonpolar solvents with a low acceptor number, AN, such as toluene, the aggregation of ionic groups with an increasing ion content reduces the reactivity. A solvent with a high value of AN, such as chloroform, led a very low reactivity independent of the ion content. Aprotic polar solvent, such as acetonitrila, promoted the dissociation of the ionic groups and furnished a relatively high reactivity independent of the ion content. Several catalytic substitution reactions were carried out under liquid-solid-solid triphase conditions. The kinetic results were accounted for in terms of slow nucleophile transport and fast chemical reaction within the ionomer particles. © 1994 John Wiley & Sons, Inc. 相似文献
72.
(±)-Ascochlorin, 5-chloro-2, 4-dihydroxy-6-methyl-3-[(2, 4)-5-(1,2,6-trimethyl-3-oxocyclohexyl)3-methyl-3,4-pentadienyl] benzaldehyde, was synthesized in 14 steps from (±)-3,4-dimethyl-2-cyclohexenone. 相似文献
73.
Photoswitching of the intramolecular magnetic interaction was demonstrated using diarylethenes with 2,5-bis(arylethynyl)-4-methyl-3-thienyl side group. Two nitroxide radicals were placed at each end of the 2,5-bis(arylethynyl)-4-methyl-3-thienyl group. Three kinds of aryl groups, 2,5-thienylene, p-phenylene, and m-phenylene groups, were used in the arylethynyl moiety. The diarylethene photoswitching units have an extended pi-conjugated chain on one side of the diarylethene. The photochromic reactivity was dependent on the arylethynyl group. Diarylethenes with m-phenylene group showed an efficient photochromic reactivity. Along with the photochromic reaction the diarylethenes showed photoswitching of an ESR spectrum originating from the change in the magnetic interaction between two unpaired electrons. The open-ring isomer showed stronger exchange interaction than the photogenerated closed-ring isomer. The magnetic interaction between two radicals via the pi-conjugated chain was altered by photocyclization due to the change of the hybrid orbital at the 2-position of the thiophene ring from sp(2) to sp(3). 相似文献
74.
Kondo M Miyazawa M Irie Y Shinagawa R Horiba T Nakamura A Naito T Maeda K Utsuno S Uchida F 《Chemical communications (Cambridge, England)》2002,(18):2156-2157
A coordination polymer [Zn(pyta)(OH)] (pyta = 4-pyridylthioacetate), was synthesized and structurally characterized; it is constructed by an alternating assembly of two types of homo-chiral helices, [Zn-OH] and [Zn-pyta], in which the sulfide moieties are fastened in the latter columns. 相似文献
75.
Kazuyoshi Yano Hiroshi Yoshitake Uwe T. Bornscheuer Rolf D. Schmid Kazunori Ikebukuro Kenji Yokoyama Yuzo Masuda Isao Karube 《Analytica chimica acta》1997,340(1-3):41-48
Piezoelectric quartz crystal sensors were developed using lipids with various properties for highly sensitive detection of chemical vapors. Lipids with varying lengths of alkyl chains were coated onto 10 MHz AT-cut quartz crystal resonators and the response of these modified crystals to chemical vapors were measured. It was shown that hydrophilic compounds, such as ethanol and methanol, could be recognized efficiently by lipids having shorter alkyl chains, whereas lipids with longer alkyl chains showed affinity to more hydrophobic vapors, such as toluene, hexane and cyclohexane. Frequency changes caused by adsorption of alcohols could be enhanced when cholesterol was co-immobilized in the lipid layer. To confirm the assumption that the sensor-response might be affected by the properties of lipids derived from acyl chains, we have examined the effects of two types of newly synthesized unusual lipids on sensor response. When lipids having one triple bond each at different positions on their alkyl chains were coated onto quartz crystals separately, lower responses were observed compared to responses obtained for a sensor with immobilized, saturated phosphatidylcholine. Lipids containing -branched acyl chains, however, showed good affinity for organic vapors, and sensor responses improved 4–5-fold. Moreover, these sensors were shown to have sensitivity of the same order as the humans' sense of smell (10−5–10−6 w/w in liquid paraffin) when measured using standard odorants (isovaleric acid, skatole, etc.) for an olfactometry established in Japan. 相似文献
76.
Hirata K Suzuki T Noya A Takei I Hidai M 《Chemical communications (Cambridge, England)》2005,(29):3718-3720
The reactions of [Cp*MCl2]2(Cp*=eta5-C5Me5, M = Rh, Ir) with thiacalix[4]arene (TC4A(OH)4) and tetramercaptothiacalix[4]arene (TC4A(SH)4) gave the mononuclear complexes [(Cp*M){eta3-TC4A(OH)2(O)2}] and the dinuclear complexes [(Cp*M)2{eta3eta3-TC4A(S)4}] respectively, while the analogous reactions with dimercaptothiacalix[4]arene (TC4A(OH)2(SH)2) produced the tetranuclear complexes [(Cp*M)2(Cp*MCl2)2-{eta3eta3eta1eta1-TC4A(O)2(S)2}]. 相似文献
77.
Toshinobu Higashimura Kenji Ebara Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》1989,27(9):2937-2950
Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I2) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?w/M?n around or below 1.1. Desilylation of the polymers under mild conditions (with H+ for MeSiVE and F? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers. 相似文献
78.
Carlos Rodríguez-Abreu Massimo Lazzari Dharmesh Varade Masaya Kaneko Kenji Aramaki Manuel Arturo López Quintela 《Colloid and polymer science》2007,285(6):673-680
The structure and rheological properties of a poly(dimethylsiloxane)-graft-poly(oxyethylene) copolymer at high concentrations
in block-selective solvents were studied by small-angle X-ray scattering (SAXS) and rheometry. Analysis of SAXS data indicates
that quasispherical, reverse micellar aggregates (with no ordered packing) are present in concentrated solutions of the copolymer
in nonpolar solvents, and that upon addition of water, the size of such aggregates increases due to the solubilization inside
the micellar cores. The viscosity of concentrated polymer solutions increases exponentially as water is added, and finally,
viscoelastic, gel-like behavior is found in the vicinity of the phase separation limit. It was found that small silver nanoparticles
with an average diameter of ≈3 nm can be synthesized inside the copolymer aggregates without the need of a reducing agent;
namely, particles embedded in a viscoelastic matrix are obtained. The synthesis seems to follow first-order kinetics.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
79.
(2R,5S)-2-Methyl-5-hexanolide and its antipode were synthesized in highly optically pure state (?98–99% e.e.) starting from ethyl (S)-lactate and the enantiomers of methyl β-hydroxyisobutyrate. The specific rotations of our samples were [α]D±91.0-93.5° (CHCl3), while the reported values of the samples prepared by resolution or asymmetric synthesis were ±64.5–65.6°. 相似文献
80.
Both the enantiomers of 2,3-dihydro-2-isopropyl-2,5-dimethylfuran were synthesized employing the Sharpless asymmetric epoxidation reaction. The (R)-(—)-enantiomer of this cyclic enol ether was also synthesized starting from (R)-(—)-linalool. 相似文献