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排序方式: 共有309条查询结果,搜索用时 46 毫秒
91.
Macroreticular chelating resins containing mercapto groups were prepared by the reaction of 2,3-epithiopropyl methacrylate/divinylbenzene macroreticular copolymer beads with ethanolic potassium hydrogensulfide solution for 1 h at 50°C. The adsorption capacities of this resin for Ag+, Hg2+, Pb2+ and Cd2+ were determined at various pH values. In the acidic region, the resin shows a high affinity for Ag+ and Hg2+ and high resistance against air oxidation. Cadmium is readily eluted with 1 mol dm?3 hydrochloric acid; silver, mercury and copper ions can be eluted with 1 mol dm?3 hydrochloric acid containing 5% (w/v) thiourea. The proposed resin appears to be useful for the removal of As3+ from aqueous solutions. 相似文献
92.
A novel method for the synthesis of N-alkyl-3-acyl-4-alkoxycarbonylmethylpyrrolidine-2,5-diones (3) was accomplished. α-Oxoketene O,N-acetals (1) reacted with maleic anhydride (2) at 80–110 °C for 5 h without solvent to give 3 in moderate to good yield (36–74%). Single X-ray crystallographic analysis showed that the two substituents on C-3 and C-4 were trans. 相似文献
93.
Masahiko Takahashi Hironori Nagaoka Kazuhiro Inoue 《Journal of heterocyclic chemistry》2004,41(4):525-530
5 or 7‐Trifluoromethyl‐1,2,3,4‐tetrahydropyrido[2,3‐d]pyrimidine‐2,4‐diones 3 , 5 , 10 , 13 and 4‐ or 6‐trifluoromethylpyrazolo[3,4‐b]pyridines 15 , 16 , 19 , 21 were prepared from 6‐aminouracils and 5‐aminopyrazoles, respectively, in good yields by the use of building blocks such as 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butanedione, 1,1,1‐trifluoro‐4‐phenyl‐3‐buten‐2‐one, 4‐ethoxy‐1,1,1‐trifluoro‐3‐buten‐2‐one, and ethyl trifluoroacetoacetate. 相似文献
94.
A cyanide-bridged molecular square of [Ru(II) (2)Fe(II) (2)(mu-CN)(4)(bpy)(8)](PF(6))(4).CHCl(3).H(2)O, abbreviated as [Ru(II) (2)Fe(II) (2)](PF(6))(4), has been synthesised and electrochemically generated mixed-valence states have been studied by spectroelectrochemical methods. The complex cation of [Ru(II) (2)Fe(II) (2)](4+) is nearly a square and is composed of alternate Ru(II) and Fe(II) ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [Ru(II) (2)Fe(II) (2)](PF(6))(4) in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one-electron redox processes of [Ru(II) (2)Fe(II) (2)](4+) right arrow over left arrow [Ru(II) (2)Fe(II)Fe(III)] (5+) right arrow over left arrow [Ru(II) (2)Fe(III) (2)](6+) right arrow over left arrow [Ru(II)Ru(III)Fe(III) (2)](7+) right arrow over left arrow [Ru(III) (2)Fe(III) (2)](8+). Electrochemically generated [Ru(II) (2)Fe(II)Fe(III)](5+) and [Ru(II) (2)Fe(III) (2)](6+) showed new absorption bands at 2350 nm (epsilon =5500 M(-1) cm(-1)) and 1560 nm (epsilon =10 500 M(-1) cm(-1)), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from Fe(II) to Fe(III) and from Ru(II) to Fe(III) ions, respectively. The electronic interaction matrix elements (H(AB)) and the degrees of electronic delocalisation (alpha(2)) were estimated to be 1090 cm(-1) and 0.065 for the [Ru(II) (2)Fe(II)Fe(III) (2)](5+) state and 1990 cm(-1) and 0.065 for the [Ru(II) (2)Fe(III) (2)](6+) states. 相似文献
95.
Hironori Kinoshita Tatsunori Iwamura Tadashi Kataoka Osamu Muraoka 《Tetrahedron letters》2005,46(42):7155-7158
(2S,3S,1′R)-2-(α-Methoxybenzyl)-3-phenyl-3-sulfanylpropionamides were diastereoselectively prepared by the reactions of N-cinnamoyl-4S-isopropyl-5,5-dimethyloxazolidinethione with acetals in the presence of SnCl4. The absolute configuration of the three newly created contiguous stereocenters was determined by the X-ray analysis of the disulfide. The amides were transformed into propanols by the reductive removal of the oxazolidinone moiety. 相似文献
96.
Recent progress in photocatalytic decomposition of water to H2 and O2 using simple oxide semiconductor catalysts has been reviewed. Addition of Na2CO3 to Pt/TiO2 suspension in water enhanced the stoichiometric decomposition significantly. This Na2CO3 addition method has been proved to be very useful to accelerate water splitting over various kinds of oxide semiconductor photocatalysts. The role of CO3 2? anion on the acceleration of water splitting was clarified. Finally, it was firstly demonstrated in the world that water was decomposed efficiently and stoichiometrically to H2 and O2 using a 3 wt% NiOx/TiO2 photocatalyst under real solar light irradiation in Tsukuba, Japan by this Na2CO3 addition method. 相似文献
97.
98.
99.
We applied laser-diode sheetlike end pumping to a multimode Nd:YVO(4) laser and observed high-speed (>400-MHz) modulation of the intensity of chaotic pulsation near 1 MHz. The frequencies of modulation were the beat frequencies for pairs of closely spaced lasing modes. Asymmetric optical confinement and the resultant modal interference are shown to lead to oval-hollow-mode operation in which modal beat notes induce high-speed modulation, the frequency range of which is 2 orders of magnitude higher than the intrinsic relaxation oscillation frequency. Good numerical reproduction of the observed chaotic pulsations and their high-speed modulation was obtained with model equations in which such effects as nonlinear gain coupling among modes and field interference between pairs of modes were included. High-speed pulsations in nonchaotic lasers were also demonstrated. 相似文献
100.