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81.
Gas mixtures of methane and ethane form structure II clathrate hydrates despite the fact that each of pure methane and pure ethane gases forms the structure I hydrate. Optimization of the interaction potential parameters for methane and ethane is attempted so as to reproduce the dissociation pressures of each simple hydrate containing either methane or ethane alone. An account for the structural transitions between type I and type II hydrates upon changing the mole fraction of the gas mixture is given on the basis of the van der Waals and Platteeuw theory with these optimized potentials. Cage occupancies of the two kinds of hydrates are also calculated as functions of the mole fraction at the dissociation pressure and at a fixed pressure well above the dissociation pressure. 相似文献
82.
Yoshiyuki Koyama Kazunari Harima Kei Matsuzaki Toshiyuki Uryu 《Journal of polymer science. Part A, Polymer chemistry》1985,23(12):2989-2998
1,4-Anhydro-2,3-di-O-benzyl-α-L -arabinopyranose (=1,5-anhydro-2,3-di-O-benzyl-β-L -arabinofuranose) (ABAP) was synthesized and underwent cationic ring-opening polymerization with several kinds of Lewis acids. All the polylmers prepared by Lewis acids as catalyst were found to consist of two different structural units, α-furanosidic and β-furanosidic units, and the structure of the polymers greatly depended on the polymerization conditions. Polymerization of ABAP with antimony pentachloride catalyst at 0°C for 42 h gave a polymer with the highest α content of 93%, and that at ?20°C for 3 h gave a polymer with the lowest (25%) α content. The other catalysts such as phosphorus pentafluoride, boron trifluoride etherate, niobium pentafluoride, and tantalum pentafluoride also afforded polymers with mixed structure of α-and β-furanosides. After debenzylation of poly(ABAP), a new polysaccharide, L -arabinofuranan was obtained. 相似文献
83.
Hitoshi Miyasaka Yuko YoshinoTomohiko Ishii Ryo KanehamaToshio Manabe Masahiro YamashitaHiroyuki Nishikawa Isao IkemotoHideo Kishida Hiroyuki MatsuzakiHiroshi Okamoto 《Journal of solid state chemistry》2002,168(2):418-426
An assembled compound (BEDT-TTF)2[Mn2Cl5(EtOH)] (1) consisting of two structural lattices of Mn(II)-Cl one-dimensional (1-D) chains and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) stacking layers was synthesized by electrochemical crystallization. Compound 1 crystallized in triclinic space group P-1 (#2) with a=13.1628(5) Å, b=20.3985(9) Å, c=7.4966(3) Å, α=98.3498(8)°, β=104.980(1)°, γ=74.602(2)°, V=1868.3(1) Å3, and Z=2. The 1-D chains and the stacking layers are aligned along the c-axis of the unit cell. The 1-D chain is described as [Mn2Cl5(EtOH)]∞− in which two Mn(II) ions and four Cl− ions form a ladder-like chain with Kagomé (cuboidal) sublattices, and the remaining Cl− ion and an ethanol molecule cap the edge-positioned Mn(II) ions of the chains. The BEDT-TTF molecules are packed between the Mn-Cl chains (ac-plane), the intermolecular S·S contacts of which are approximately found in the range 3.440(2)-3.599(2) Å. The packing feature of BEDT-TTF molecules is very similar to that of (BEDT-TTF)2ClO4(TCE)0.5 (TCE=1,1,2-trichloroethane) (J. Am. Chem. Soc., 105, 297 (1983)). Regarding the electronic state of each BEDT-TTF molecule, Raman spectroscopic analysis and ESR study revealed the presence of half-valence BEDT-TTF molecules (charge delocalization) in 1. Magnetic measurements clearly demonstrated that the paramagnetic spins on the 1-D chain [Mn2Cl5(EtOH)]∞− arrange antiferromagnetically in the low-temperature region. Additionally, 1 exhibits metallic conductivity in the temperature range 2.0-300 K (σ=21 S cm−1 at 300 K and 1719 S cm−1 at 2.0 K), due to the contribution of the stacked BEDT-TTFs. Consequently, these peculiarities that correspond to antiferromagnetic/metallic conductivity demonstrate the “bi-functionality” of 1. 相似文献
84.
A simple and sensitive method is described for the determination of biogenic indole compounds adsorbed on cellulose or alumina plates for thin-layer chromatography by room-temperature phosphorimetry. The optimum conditions were investigated for 5-hydroxyindole-3-acetic acid and indole-3-acetic acid. The compounds are spotted on the plates, which are then sprayed successively with sodium citrate or sodium acetate, and sodiu iodide solutions. The plates are dried completely under a stream of dry nitrogen, and immediately dipped in molten paraffin. The phosphorescence is stable for at least 3 h even in moist air. The limits of detection for nine biogenic indole compounds tested are between 2 and 300 pmol per sample spot. 相似文献
85.
Takashi Tozawa Dr. Hitoshi Nagao Yoshinobu Yamane Teruaki Mukaiyama Prof. Dr. 《化学:亚洲杂志》2007,2(1):123-134
Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine‐derived catalyst that bears both a sterically hindered N1‐9‐anthracenylmethyl group and a strongly electron withdrawing 9‐O‐3,5‐bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and α,β‐unsaturated ketones followed by lactonization. Optically active 3,4‐dihydropyran‐2‐one derivatives were obtained in high yields with excellent control of enantio‐ and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month. 相似文献
86.
Tsuneyuki Sato Shukei Inui Hitoshi Tanaka Tadatoshi Ota Mikiharu Kamachi Kohji Tanaka 《Journal of polymer science. Part A, Polymer chemistry》1987,25(2):637-652
The polymerization of di-n-butyl itaconate (DBI) intiated with AIBN was kinetically investigated in benezene. The polymerization rate (Rp) was expressed by: Rp = k[AIBN]0.5[DBI]1.7. The polymerization showed a considerably low overall activation energy of 15.3 kcal/mol. The initiator efficiency of AIBN in this system decreased with increasing DBI concentration, ranging from 0.34 to 0.55°C, which is ascribable to viscosity effect due to the monomer. From an ESR study, the polymerization system was found to involve two kinds of persistent radicals, namely, primary propagating ( III ) and propagating ( I ) radicals. The relative concentration of III to I increased with decreasing monomer concentration. Azo-nitrile initiators such as AVN and ACN similarly produced two persistent radicals, while MAIB, DBPO, and PBO yielded only propagating radical I as persistent. The MAIB-initiated polymerization of DBI was also performed in benzene. Similar kinetic features were observed, that is, a higher dependence of Rp on the DBI concentration and a low overall activation energy (14.4 kcal/mol). The following rate equation was obtained at 50°C:Rp = k[MAIB]0.5[DBI]1.6. The initiator efficiency of MAIB decreased with increasing DBI concentration, ranging from 0.32 to 0.53 at 50°C. The concentration of propagating radical I was determined by ESR at 50 and 61°C, from which kp and kt were estimated. The kp value increased with increasing monomer concentration, while the kt one decreased with the DBI concentration. These values are much lower compared with those of MMA. 相似文献
87.
Kiyoshi Hasebe Satoshi Hikima Hitoshi Yoshida 《Fresenius' Journal of Analytical Chemistry》1991,339(4):261-263
Summary The covalent bonding of l-lactate oxidase (no E.C.) to cross-linked copolymers of chitosan (Chitopearl) using the glutaraldehyde method is described and applied to the determination of l-lactate in serums of diseased and normal animals. The bioreactor packing of the immobilized enzyme is stable for at least 4 months and can be continuously used for the rapid and simple determination of l-lactate. The reduction current of pyruvate, corresponding to the product of enzymatic reaction, is determined by differential pulse polarography. The reproducibility (RSD) for 10 mol/l l-lactate is 0.78% (n=6) and the detection limit is 0.62 mol/l (k=2, confidence level 97.72%). 相似文献
88.
Seiko Nan'ya Etur Maekawa Hitoshi Hayakawa Yukio Kitaguchi Yoshio Ueno 《Journal of heterocyclic chemistry》1985,22(6):1483-1485
The 5H-pyrido[2,3-a]phenoxazin-5-one derivatives and 5H-pyrido[3,2-a]phenoxazin-5-one derivatives were prepared by the condensation of substituted 2-aminophenols with 6,7-dibromo-5,8-quinolinequinone followed by dehalogenation in the presence of sodium hydrosulfite dissolved in aqueous pyridine under a nitrogen atmosphere. 相似文献
89.
Miyasaka H Nezu T Sugimoto K Sugiura K Yamashita M Clérac R 《Inorganic chemistry》2004,43(18):5486-5488
Heterometallic linear tetramers [Mn(5-R-saltmen)Ni(pao)(bpy)(2)](2)(ClO(4))(4) (5-R-saltmen(2-) = N,N'-1,1,2,2-tetramethylethylene bis(5-R-salicylideneiminate); pao(-) = pyridine-2-aldoximate; bpy = 2,2'-bipyridine, R = H, 1; Cl, 2; Br, 3; MeO, 4) have been synthesized and structurally characterized. These compounds exhibit a [Ni(II)-NO-Mn(III)-(O)(2)-Mn(III)-ON-Ni(II)] skeleton where -ON- is an oximate bridge between Mn(III) and Ni(II) ions and -(O)(2)- is a bi-phenolate bridge between Mn(III) ions. These tetramers can be seen as oligomeric units of the heterometallic Mn(III)(2)-Ni(II) chain observed in a family of single-chain magnets (Clérac, R.; Miyasaka, H.; Yamashita, M.; Coulon, C. J. Am. Chem. Soc. 2002, 124, 12837. Miyasaka, H.; Clérac, R.; Mizushima, K.; Sugiura, K.; Yamashita, M.; Wernsdorfer, W.; Coulon, C. Inorg. Chem. 2003, 42, 8203.). Magnetic measurements on these tetramers confirm the nature of the magnetic interactions reported for the Mn(III)(2)-Ni(II) chains: a strong antiferromagnetic Mn(III)/Ni(II) coupling via the oximate bridge (J(Ni-Mn) ranges from -23.7 to -26.1 K) and a weak ferromagnetic Mn(III)/Mn(III) coupling through the bi-phenolate bridge (J(Mn-Mn) ranges from +0.4 to +0.9 K). These magnetic interactions lead to tetramers with an S = 2 ground state. 相似文献
90.
Koichiro Koyama Yusuke Hirasawa Tomohiro Hoshino Norimichi Nakahata 《Tetrahedron》2005,61(15):3681-3690
Seven new Lycopodium alkaloids, lannotinidines A-G (1-7), have been isolated from the club moss Lycopodium annotinum and L. annotinum var. acrifolium. Stereochemistry of 1-7 was elucidated by combination of NOESY correlations and chemical transformation. Lannotinidines B-E (2-5) elevated NGF mRNA expression. 相似文献