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31.
The heat of immersion in water was measured at 25°C for three iron(III) oxides using a twin-type microcalorimeter. One of the samples was commercial α-Fe2O3 (sample C) and the other two (samples M and F) were prepared by calcining magnetite and iron(III) hydroxide in air at various temperatures, Tp, from 300 to 700°C. The samples were evacuated at outgassing temperature, To, between room temperature and 500°C at a pressure of 1 × 10?2?2.7 × 10?2N m?2 for 6 h. The heat of immersion, hi(J m?2), of samples C and M increased with an increase in To and showed the maximum hi at To =400°C, while sample F did not show the maximum up to To =500°C. The systematic correlation was not observed between hi and Tp of sample F. The heat of reproduction of the surface hydroxyl group on sample F was approximately estimated as 6.6 × 104 J mole?1 H2O. 相似文献
32.
Hidefumi Hirai Tsuneaki Tanabe Hideomi Koinuma 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):203-222
Triad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of 1H- and 13C-NMR. The cotacticities from 1H-NMR spectra are obtained accurately by using α-d-styrene in the place of styrene and by measuring the spectra on the copolymer in o-dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis-Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the 1H- and 13C-NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C1 carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f2Y - 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C1 carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first-order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex. 相似文献
33.
Masaaki Fujimatsu Tadao Natsuume Hirotaka Hirata Yasuhiko Shirota Shigekazu Kusabayashi Hiroshi Mikawa 《Journal of polymer science. Part A, Polymer chemistry》1970,8(11):3349-3357
Copolymerizations of N-vinylcarbazole with both isobutyl vinyl ether and N-vinyl-pyrrolidone initiated by some organic electron acceptors have been investigated for the purpose of elucidating the propagation mechanism in the charge-transfer polymerization. Copolymerizations of the same system catalyzed by authentic cationic catalysts have also been made for comparison. The results indicate that the propagation mechanism of the charge-transfer polymerization studied is catio ie. 相似文献
34.
Yasushi OgawaMasahito Toyama Michinori KarikomiKazuo Haga Tadao Uyehara 《Tetrahedron letters》2003,44(10):2167-2170
Both enantiomers of (P)-(+)-2- and (M)-(−)-2-acetoxy-11,14-dimethyl[5]helicenes 8 were synthesized by asymmetric aromatic oxy-Cope rearrangement of the corresponding chiral bridged bicyclic compounds, which were obtained by enzymatic resolution. The absolute configurations of 8 were assigned by their circular dichroism spectra. 相似文献
35.
Although methanolysis of [α-(trimethylsilyl)benzyl]ferrocene (I) and [p-methyl-α-(trimethylsilyl)benzyl]ferrocene (II) in the presence of anhydrous ferric chloride merely gave α-ferrocenylbenzyl methyl ether (III) and p-methyl-α-ferrocenylbenzyl methyl ether (IV), respectively, acid-catalyzed methanolysis of (I) and (II) in the presence of an equimolar amount of (III) or (IV) afforded 1,2-diferrocenyl-l,2-diarylethanes. It is suggested that one electron oxidation of [α-(trimethylsilyl)benzyl]ferrocene by α-ferrocenylbenzyl cation generated from α-ferrocenylbenzyl methyl ether, and subsequent methanolysis of the resulting substituted ferricenium ion may occur to give the two species of α-ferrocenylbenzyl radical, which in turn undergo an approximately statistical coupling. 相似文献
36.
Yahachi Saito Tadao Koyama Kenichiro Kawabata 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,40(1):421-424
Single-layer (SL) carbon tubes were produced by arc evaporation of graphite rods containing iron-group metals (Fe, Co, Ni, Fe/Co, Co/Ni, Fe/Ni) under He and Ar gas. Transmission electron microscopy (TEM) revealed that these elemental and binary metals, excluding Fe which need a special atmosphere (a mixture of Ar and CH4), showed catalytic activity producing SL tubes under pure inactive gases. Fe/Ni alloy was the most effectual catalysts for producing SL tubes. The highest abundance of SL tubes in raw soot was estimated to be ~ 10% from TEM observation. Smoke particles directly caught on TEM grids near an evaporation source during arcburning were also investigated, and it was suggested that small metal particles were first formed in the gas phase and then SL tubes grew from them. 相似文献
37.
Kazunori WakasugiAtsushi Nakamura Akira IidaYoshinori Nishii Nobuji NakataniShoji Fukushima Yoo Tanabe 《Tetrahedron》2003,59(28):5337-5345
Various carboxylic esters or amides were prepared in good to excellent yield between carboxylic acids and equimolar amounts of alcohols or amines under very mild conditions (0-45°C; within 3 h) using dimethylsulfamoyl chloride (Me2NSO2Cl; 1) combined with N,N-dimethylamines (Me2NR: 2a; R=Me, 2b; R=Bu). The choice of the sulfamoyl chloride and the amine is crucial for the reaction; that is, sterically uncrowded amines accelerated the present esterification and amidation. This agent had some advantages over methanesulfonyl chloride (3)/amines as for the atom-economy, avoidance of side reactions, and had very high chemoselectivity toward the carboxyl group vs the hydroxyl group; the experiment was performed by the addition of 1 to the mixture of carboxylic acids and alcohols. Application of this method to the synthesis of coumaperine, a chemopreventive natural product, was performed using the present amidation as a key step. 相似文献
38.
Kawai K Osakada Y Takada T Fujitsuka M Majima T 《Journal of the American Chemical Society》2004,126(40):12843-12846
A series of naphthalimide (NI)- and 5-bromocytosine ((br)C)-modified oligodeoxynucleotides (ODNs) were prepared, and their lifetimes of the charge-separated states during the photosensitized one-electron oxidation of DNA were measured. Various lifetimes of the charge-separated states were observed depending on the sequence and the incorporation sites of (br)C, and the oxidation potential of G in the (br)C:G base-pair relative to that of G in the C:G base-pair and in the GGG sequence was determined by comparing the lifetimes of the charge-separated states. The change in the cytosine C5 hydrogen to bromine resulted in a 24 mV increase in the oxidation potential of G in the (br)C:G base-pair as compared to that of G in the C:G base-pair, the value of which is comparable to a 58 mV decrease in the oxidation potential of G in the GGG sequence. These results clearly demonstrate that hole transfer in DNA can be controlled through hydrogen bonding by introducing a substituent on the cytosine. 相似文献
39.
Yuzuru Katagiri Kenzo Kanohta Kazuhiko Nagasawa Tadao Okusa Toshio Sakai Osamu Tsumura Yasuhiko Yotsui 《Analytica chimica acta》1981,133(4):535-543
A practical search system for proton n.m.r. spectra is reported. The coding rules and search algorithms are described in detail. Data for 8000 spectra have been converted into a computer-readable file from printed charts. Several search tests are used to evaluate the usefulness of the search system, and various effects of experimental conditions such as different instruments, frequencies and solvents on recall efficiency are described. The results presented indicate that the system should be applicable to routine analytical work. 相似文献
40.
Tongbu Lu Xin Wang Minyu Tan Yu Liu Yoshihisa Inoue Tadao Hakushi 《Helvetica chimica acta》1993,76(1):241-247
The lanthanide nitrate complexes with 13-crown-4(13-C-4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO3)3.(13-c-4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and 1H-NMR spectra, conductivity measurements, and TG-DTA techniques. The crystal and molecular structure of Nd(No3)3. (13-c-4) has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 Å3, Dc = 2.01 g cm?3, μ = 31.0 cm?1 (Mok2), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.032 for 5218 independent reflections with I ? 3σ(I). There are two independent Nd(No3)3 · (13-C-4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers. 相似文献