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991.
Jeferson G. da Silva Lucas S. Azzolini Solange M.S.V. Wardell James L. Wardell Heloisa Beraldo 《Polyhedron》2009
Reaction of N(4)-phenyl-2-formylpyridine thiosemicarbazone (H2Fo4Ph), N(4)-phenyl-2-acetylpyridine thiosemicarbazone (H2Ac4Ph) and N(4)-phenyl-2-benzoylpyridine thiosemicarbazone (H2Bz4Ph) with gallium nitrate gave [Ga(H2Fo4Ph)2](NO3)3 (1), [Ga(2Ac4Ph)2]NO3 (2) and [Ga(2Bz4Ph)2]NO3 (3). In all complexes coordination of the thiosemicarbazone via the Npy–N–S chelating system occurs. In 1 the thiosemicarbazone acts as a neutral ligand while in 2 and 3 the ligand is anionic. Upon slow diffusion of 2 in DMSO [Ga(2Ac4Ph)2]NO3·DMSO (2a) was formed. The crystal structure of 2a was determined. Upon coordination the antibacterial activity of both gallium and thiosemicarbazones against Pseudomonas aeruginosa significantly increases. 相似文献
992.
Wagner José Barreto Sonia Regina Giancoli Barreto Waleria Pickina Silva 《Transition Metal Chemistry》2009,34(6):677-681
The reaction between Fe(III) and dopamine in aqueous solution in the presence of Na2S2O3 was followed through UV–Vis spectroscopy, pH and oxy-reduction potential (Eh) measurements. The formation and quick disappearing
of the complex [Fe(III)HL1−]2+, HL1− = monoprotonated dopamine was observed with or without S2O3
2− at pH 3. An unexpected reaction occurs in presence of thiosulfate forming the stable anion complex [Fe(III)(L2−)2]1−, L2− = dopacatecholate (λ = 580 nm) and the auto-increasing of the pH, from 3 to 7. It was proposed that H+ and molecular oxygen are consumed by free radical thiosulfate formed during the reaction. 相似文献
993.
Valderes Moraes de Almeida Alexandre José da Silva Góes Carlos Roque Duarte Correia 《Tetrahedron letters》2009,50(6):684-687
Novel aza-bicyclic 2-isoxazolines, 4,5-dihydroisoxazole[5,4-b]pyrrolidines, and 4,5-dihydroisoxazole[5,4-b]piperidines were synthesized in a highly regioselective manner through a 1,3-dipolar cycloaddition reaction of 5- and 6-membered endocyclic enecarbamates and enamides with several nitrile oxides in good to excellent yields. Hydrogenolysis of 5- and 6-membered Cbz-cycloadducts led to secondary amines, which presented distinctive stabilities. 2-Isoxazoline bisamides were obtained in good yields through a N-benzoylation, followed by ammonolysis of the secondary amine, or directly from ammonolysis of the cycloadducts. 相似文献
994.
Eufrânio N. da Silva Júnior Kelly C.G. de Moura Claudia J. Nascimento Antônio V. Pinto 《Tetrahedron letters》2009,50(14):1575-2418
The structure of ‘lapachol peroxide’ was published by Hooker in 1936; however, we recently discovered a mistake in the originally proposed structure; the correct structure, according to X-ray spectroscopy, is given here. 相似文献
995.
Homoallylic alcohols (primary, secondary, or tertiary containing an endocyclic or an exocyclic double bond) react with equimolar amounts of aldehydes (aliphatic or aromatic) and ketones (aliphatic) in the presence of 5 mol % of iodine. This Prins cyclization was used in the preparation of hexahydrobenzo[f]isochromenes and of a 4-hydroxy-tetrahydropyran, in 54-81% yield. The procedure is also efficient for an aza-Prins cyclization of a homoallylic sulfonamide and benzaldehyde, producing a hexahydrobenzo[f]isoquinoline. 相似文献
996.
T. Pinheiro A. Barreiros L. C. Alves M. Neres R. Fleming J. N. Silva P. Filipe R. Silva 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(2):161-164
Skin as a manageable organ can provide direct or indirect information of tissue iron overload resulting from inherited disorders
as hemochromatosis. Patients with hemochromatosis were evaluated at three consecutive phases along the therapy programme.
Nuclear microprobe techniques were used to assess skin iron and Total Reflection X-ray Fluorescence to determine the plasma
iron concentrations. Results showed that iron pools were differently correlated at the three therapy phases. These variations
highlighted the value of skin iron content to assess organ iron deposition and therapy efficacy. Skin iron content can be
used for a better management of patients with iron overload pathologies. 相似文献
997.
Alachlor has been widely used in agriculture all over the world. It is suggested that it may be a carcinogen and an environmental
estrogen. The aim of this work was to verify the degradation the alachlor by gamma radiation. Gamma radiation from 60Co was used to degrade the alachlor herbicide in water and methanol solution. The alachlor in water and alcohol solution in
the concentration of 100 mgL−1 was irradiated with doses of 0.25–50 kGy, at dose rate 5–6 and 2.7 kGyh−1. High performance liquid chromatography was used as an analytical technique to determine the degradation rate of herbicide
studied. 相似文献
998.
Fernanda V.M. Pontes Delmo S. Vaitsman Lílian I.D. da Silva Maria Inês C. Monteiro 《Analytica chimica acta》2009,632(2):284-59
The total Kjeldahl nitrogen (TKN) method was simplified by using a manifold connected to a purge-and-trap system immersed into an ultrasonic (US) bath for simultaneous ammonia (NH3) extraction from many previously digested samples. Then, ammonia was collected in an acidic solution, converted to ammonium (NH4+), and finally determined by ion chromatography method. Some variables were optimized, such as ultrasonic irradiation power and frequency, ultrasound-assisted NH3 extraction time, NH4+ mass and sulfuric acid concentration added to the NH3 collector flask. Recovery tests revealed no changes in the pH values and no conversion of NH4+ into other nitrogen species during the irradiation of NH4Cl solutions with 25 or 40 kHz ultrasonic waves for up to 20 min. Sediment and oil free sandstone samples and soil certified reference materials (NCS DC 73319, NCS DC 73321 and NCS DC 73326) with different total nitrogen concentrations were analysed. The proposed method is faster, simpler and more sensitive than the classical Kjeldahl steam distillation method. The time for NH3 extraction by the US-assisted purge-and-trap system (20 min) was half of that by the Kjeldahl steam distillation (40 min) for 10 previously digested samples. The detection limit was 9 μg g−1 N, while for the Kjeldahl classical/indophenol method was 58 μg g−1 N. Precision was always better than 13%. In the proposed method, carcinogenic reagents are not used, contrarily to the indophenol method. Furthermore, the proposed method can be adapted for fixed-NH4+ determination. 相似文献
999.
Roberta E.S. Froes Waldomiro Borges Neto Nilton C. Silva José B.B. da Silva 《Microchemical Journal》2009,92(1):68-72
A 23 factorial design and a CCD (Central Composite Design) were employed to optimize the operational conditions for determining Al, Ba, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Pb, Sn and Zn in soft drink samples by inductively coupled plasma optical emission spectrometry (ICP OES). Satisfactory parameters of merit were obtained (Plasma stability, linearity, SBR, BEC, LOD and LOQ). The accuracy was evaluated by means of a recovery study. Thirty five soft drink samples were analyzed. The results obtained were used in an exploratory analysis, in which principal component analysis and cluster analysis were applied in order to differentiate the several soft drink classes. Adequate LOQ values were obtained for all elements (0.34 μg L− 1 for Ca to 88.7 μg L− 1 for Mg) and the recovery study results ranged between 80 and 100%. Cluster analysis revealed four sample classes characterized by flavor and other characteristics, such as being light, diet, low calorie or regular beverages. A model with 4 PCs was obtained by means of a principal component analysis, which explained 99.8% of the total variance. 相似文献
1000.
Synthesis of pseudo-C-nucleosides from β-formyl-α,β-unsaturated ester bearing a β-furanosidic moiety
Jorge M. Pinheiro M. Isabel Ismael J. Albertino Figueiredo Artur M. S. Silva 《Monatshefte für Chemie / Chemical Monthly》2009,46(6):1237-1244