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31.
Hisao Yokota Yozo Otsuka Tsutomu Kagiya Kenichi Fukui 《Journal of polymer science. Part A, Polymer chemistry》1967,5(11):2825-2834
A kinetic study of the γ-ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to ?17°C. Two modes of the polymerization, spontaneous and γ-ray polymerization, occur in this system. The γ-ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ-ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ-ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ-radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ-ray polymerization were also investigated. 相似文献
32.
A simple method for the rapid and simultaneous analysis of dichlorvos (DDVP), malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid (2,4-D) in citrus fruit, which uses flow-injection ion spray ionization tandem mass spectrometry, has been developed for the first time. The method involves the combined use of stable isotopically labeled internal standards (DDVP-d6, malathion-d10, carbaryl-d7, and 2,4-D-d5) and a multiple reaction monitoring technique. The average recoveries for the pesticides at the same concentrations as their tolerance levels (DDVP: 0.1-0.2 μg g−1; malathion: 0.5-4.0 μg g−1; carbaryl: 1.0 μg g−1; 2,4-D: 1.0-2.0 μg g−1) ranged from 90 to 119% with the relative standard deviation (R.S.D.) ranging from 1.0 to 13.1% (n = 5). Analysis time, including sample preparation and determination, was only 15 min. The present method is effective for screening DDVP, malathion, carbaryl, and 2,4-D in citrus fruit. 相似文献
33.
Oka H Suzuki M Harada K Iwaya M Fujii K Goto T Ito Y Matsumoto H Ito Y 《Journal of chromatography. A》2002,946(1-2):157-162
pH-Zone-refining counter-current chromatography was successfully applied to the separation of the main components of Food Color Red No. 106 (R-106, acid red, Color Index No. 45100). A 300-mg quantity of sample was separated using the following two-phase solvent system: n-butanol-water, 40 mM sulfuric acid in organic stationary phase and 30 mM ammonia in aqueous mobile phase. The obtained fractions were analyzed by high-performance liquid chromatography and fast atom bombardment mass spectrometry. The separation yielded 261.9 mg of main component of acid red with purity of 99.9%. 相似文献
34.
Ohno H Ando K Hamaguchi H Takeoka Y Tanaka T 《Journal of the American Chemical Society》2002,124(51):15255-15266
The base-mediated intramolecular amination of bromoallenes having an axial chirality is described. The treatment of (4S,aR)-4-alkyl-4-[N-(arylsulfonyl)amino]-1-bromobuta-1,2-dienes with NaH in DMF affords 2,3-cis-2-ethynylaziridines in good to excellent selectivity (2,3-cis:trans = 92:8-99:1). The reaction of (4S,aS)-bromoallenes with NaH/DMF also gives 2,3-cis-2-ethynylaziridines selectively (79:21-91:9). These experimental results have been rationalized by B3LYP density functional calculations together with the 6-31+G(d) basis set and the Onsager solvation model. The transition structures for cis-aziridine formation of both (4S,aR)- and (4S,aS)-bromoallenes in DMF are favored over the corresponding trans transition structures by 4.35 and 1.41 kcal/mol, respectively. Furthermore, the calculations predicted that a less polar solvent gives higher cis selectivity for (4S,aS)-bromoallenes. In fact, improvement of the cis selectivity to 99:1 has been realized by using a less polar solvent such as THF. The cyclization of bromoallenes bearing a beta- or gamma-amino group also affords four- and five-membered azacycles in a highly cis-selective manner. 相似文献
35.
Hisao Nakatat Masataka Ishibashi Masahiro Itoh Hiroshi Miyazaki 《Journal of mass spectrometry : JMS》1987,22(1):23-29
A reaction of N,O-bis-(diethylhydrogensilyl) trifluoroacetamide with 5β-pregnane-17,20,21-triols afforded diethylhydrogensilyl (DEHS) cyclic diethylsilylene (DES) derivatives. 5β-Pregnane-3α,17α,20β,21-tetraol yielded the 3α,21-bis-DEHS-17α,20β-DES compound, whereas the structure of the major product from its 20α isomer was assigned as the 3α,17α-bis-DEHS-20α,21-DES derivative, which would undergo facile isomerization to the unstable 3α,21-bis-DEHS-17α,20α-DES structure under electron ionization. Fragmentations of these DEHS-DES compounds are discussed on the basis of isotope labelling experiments, linked scanning data, and accurate mass measurements. 相似文献
36.
Hisao Yokota Masatsune Kondo Tsutomu Kagiya Kenichi Fukui 《Journal of polymer science. Part A, Polymer chemistry》1968,6(2):425-434
A cationic polymerization of formaldehyde which gave a high molecular weight polymer was studied in liquid carbon dioxide at 20–50°C. In the polymerization without any catalyst both the rate of polymerization and the molecular weight of the resulting polymer increased rapidly with a decrease in the loading density of the monomer solution to the reaction vessel, and also increased with an increase in the initial monomer concentration. From these results it was concluded that the initiating species could be ascribed to an impurity contained in the monomer solution. Both the rate of polymerization and the degree of polymerization of the polymer also increased with rising temperature. The carboxylic acid added acted as a catalyst in the polymerization because of increase in the polymer yield, the molecular weight of polymer formed, and the number of moles of polymer chain with increasing dissociation constant of acid used. It was concluded that the polymerization in liquid carbon dioxide proceeded by a cationic mechanism. Methyl formate had no influence on the polymerization, but methanol and water acted as a chain-transfer agent. 相似文献
37.
Oki Michinori Toyofuku Yoshitaka Sakaue Tatsuya Hirose Takanori Asakura Mitsuhiro Morita Nobuhiro Toyota Shinji 《Russian Journal of Organic Chemistry》2003,39(4):542-553
X-ray crystallography of the ap-form of the 1-(9-fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene has revealed that the carbon atom of the oxirane which is connected to the naphthyl group in this compound is almost planar. The specific structural features of the epoxy ring in this compound are caused by sterical effects and by the presence of a -system in the immediate vicinity of the oxirane ring. Certain differences have been found also in reactivity of rotational isomers of 2-X-substituted 1-[1-(9-fluorenyl)-2-naphthyl]ethyl cations (X = O, S, Se). At X = O arose more deprotonation product from the -position of the oxygen than in reactions of sulfur and selenium-containing analogs. Reactions of epoxides with zinc chloride almost exclusively gave the corresponding aldehydes. 相似文献
38.
Jun-Ichi Asakura Masakuni Yoshihara Takaaki Shindo Yoshio Matsubara Toshihisa Maeshima 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):371-377
The radical copolymerization of vinylidene chloride (Vc, M1) with 3(2-methyl)-6-methylpyridazinone (I, M2) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r1 against those of V C[dbnd]O and V C[dbnd]C of monomers determined in the solvents. 相似文献
39.
40.
Yoshitaka Yoda Yasuhiko Imai Hisao Kobayashi Syunji Goto Kunikazu Takeshita Makoto Seto 《Hyperfine Interactions》2012,206(1-3):83-86
An Upgrade of the nuclear resonant scattering beamline, BL09XU in SPring-8 has been conducted. A liquid nitrogen cooled high-heat load monochromator was installed and a 2nd experimental hutch was constructed. The instruments installed in the hutch allow for a variety of sample conditions. Newly developed high-resolution monochromators with better stability including the back scattering geometry monochromator have opened up the easy access to more isotopes and more precise measurements. 相似文献