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991.
992.
Heimei Yuki Yoshio Okamoto Koji Ohta Koichi Hatada 《Journal of polymer science. Part A, Polymer chemistry》1975,13(5):1161-1174
Monomer reactivity ratios, r1 and r2 were determined in the anionic copolymerizations of methyl methacrylate (MMA, M1) with ethyl (EtMA), isopropyl (i-PrMA), tert-butyl (t-BuMA), benzyl (BzMA), α-methylbenzyl (MBMA), diphenylmethyl (DPMMA), α,α-dimethylbenzyl (DMBMA), and trityl (TrMA) methacrylates (M2) by use of n-BuLi as an initiator in toluene and THF at -78°C. The order of the reactivity of the monomers towards MMA anion was DPMMA > BzMA > MMA > EtMA > MBMA > i-PrMA > t-BuMA > TrMA > DMBMA in toluene and TrMA > BzMA > MMA > DPMMA > EtMA > MBMA > i-PrMA > DMBMA > t-BuMA in THF. Except for the extremely low reactivity of TrMA and DPMMA in toluene due to steric hindrance, the order was explained in terms of the polar effect of the ester groups. A linear relationship was found between log (1/r1) and Taft's σ* values of the ester groups, where the ρ* value was 1.1. The plots of log (1/r1) vs. the 1Ha (cis to the carbonyl) and 13Cß chemical shifts of the monomers were also on straight lines. The polymer obtained in the copolymerization of MMA with TrMA in toluene by n-BuLi at -78°C was a mixture of poly-MMA and a copolymer, suggesting that there exist two kinds of growing centers. 相似文献
993.
Nakamura T Yasuda S Miyamae T Nozoye H Kobayashi N Kondoh H Nakai I Ohta T Yoshimura D Matsumoto M 《Journal of the American Chemical Society》2002,124(43):12642-12643
Dialkyl ditellurides adsorb on Au(111) surfaces by wet deposition to form highly resistive autooxidized monolayers (AMs) due to the automatic formation of oxidized tellurium species after the adsorption of ditellurides on the surfaces under air in contrast to the case of the lighter dichalcogenides such as disulfides and diselenides. The ditelluride AMs could be applied to the selective fabrication of effective resistance, ferroelectric layers, piezoelectric parts, and/or new imaging systems using the feature of tellurium oxide in small device circuits. 相似文献
994.
Takeuchi T Tatsumi S Masuoka S Hirose K Uzu H Jin JY Fujimoto C Ohta K Lee KP Ryoo JJ Choi SH 《Journal of chromatography. A》2003,1021(1-2):55-59
Split flow and bypass flow systems were assembled using Nano Y Connectors with low dead volume commercially available for capillary liquid chromatography (LC). The split ratio could be controlled by changing the dimension of restriction tubing and applied back pressure to the restriction tubing. The split flow system allowed us to use valve injectors and pumps commercially available for capillary LC. The reproducibility of the present split flow system was acceptable. The relative standard deviation for six successive measurements was 0.4% for the retention time, whereas that for the peak height and peak area was 1-3% depending on the analytes. The bypass flow system uses two Nano Y Connectors, where the eluent split at the first Nano Y Connector, which is located in the inlet of the separation column, is merged again into the effluent from the column at the second Nano Y Connector. The bypass flow system could avoid on-column detection and allowed us to use flow cells, leading to an approximate three times improvement in signal-to-noise. The present flow systems were evaluated by using aromatic hydrocarbons and alkylbenzenes as test analytes. 相似文献
995.
[reaction: see text]. A new group-selective reaction is described, that is, the hydroalumination of bis-alkynyl alcohols armed with an adjacent stereogenic center, giving stereo-defined tert-alcohols of potential utility in natural product synthesis. 相似文献
996.
997.
Variations of natural 13C and 15N abundances in the rat tissues and their correlation 总被引:1,自引:0,他引:1
The 13C and 15N abundances of the tissues of rats fed with a constant diet were measured by mass spectrometry. Isotopic discrimination was larger in 15N than in 13C compared to diet. The extents of discrimination of 13C and 15N differed depending on tissues, but highly correlated each other. 相似文献
998.
Akihiro Ohta Tokuhiro Watanabe Yasuo Akita Maki Yoshida Suzumi Toda Tomoko Akamatsu Hiroko Ohno Akiko Suzuki 《Journal of heterocyclic chemistry》1982,19(5):1061-1067
The reactions of the monoxides of propylpyrazine and phenylpyrazine with phosphoryl chloride or acetic anhydride were investigated. Except in the case of the reaction of 2-propylpyrazine 1-oxide with acetic anhydride, chlorination or acetoxylation occurred on the pyrazine ring in all cases; moreover, these reactions occurred preferentially at the position poorest in π-electron density. The N-oxidation and the successive chlorination of monochloro-phenylpyrazines were also investigated, and the structures of the products were confirmed. 相似文献
999.
1000.