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991.
The kinetics of the oxidation of benzyl alcohol by potassium chlorochromate, KCrClO3, has been studied in dimethyl sulfoxide-dichloromethane medium. The reaction is catalyzed by acid. The effects of temperature and solvent composition were studied and activation parameters evaluated. Probable mechanisms are discussed.
, KCrClO3, . . . .相似文献
992.
A simple reverse flow-injection (rFIA) manifold for the direct determination of aluminum in drinking water is proposed. This rapid and sensitive method is based on the formation of an Al(3+) complex with salicylaldehyde picolinoylhydrazone (SAPH), which shows a maximum blue-green fluorescence (lambda(ex)=384 nm, lambda(em)= 468 nm) at pH 5.4. Operative conditions both for batch and rFIA procedures were investigated including reagent concentration, buffer solutions, injection loop, reacting coil and wavelengths used for the fluorimetric detection. The tolerance limits of foreign ions have been also evaluated, before and after the addition of masking agents. The reverse flow-injection procedure allows determination of Al(3+) at ppb level (LOD: 1.9 mug l(-1)) within a working range of 5-30 mug l(-1). The proposed method was successfully employed for the determination of Al(3+) in several commercial drinking, soft drinking (as certified reference material), and tap water samples. 相似文献
993.
Viktoriya V. Skripacheva Ella Kh. Kazakova Nelly A. Markarova Vladimir E. Kataev Ludmila V. Ermolaeva Wolf D. Habicher 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):77-81
The binding of different sized and shaped metal complexes [Co(His)2]ClO4(1), [Co(en)2C2O4]Cl (2) and [K18-crown-6]SCN (3)(en-ethylendiamine, His-L-histidynate-anion) with a new tetrasulfonatomethylcalix[4]resorcinarene([H8X]Na4) was investigated in neutral and alkaline aqueous media by NMR and pH-metrictitration methods and compared with those of recently studied NMe4Br (4). The resultsobtained indicate that the outer-sphere coordination of complexes 1–3 by[H8X]4- proceeds via the interaction of hydrophobic fragments of the guestswith both the negatively charged rim and the hydrophobic cavity as a -base. Thenature of binding does not change for cations 1, 2 and 4 on going from[H8X]4- in neutral to [H4X]8- in alkaline media, while the inclusionof 3 decreases on going from [H8X]4- to [H4X]8-. 相似文献
994.
Belén Abarca Rafael Ballesteros Gurnos Jones 《Journal of heterocyclic chemistry》1984,21(6):1585-1588
A synthesis of the methylthieno[3,2-c]cyclohepteno[b]indole 7 from 2-methylthieno[3,2-b]cycloheptanone 3 is described. Unsuccessful attempts to prepare the isomeric thienocycloheptenoindole system present in formula 2 , from the dihydrobenzothiophenone 8 , and from derivatives of 5-(2-thienyl)-4-oxopentanoic acid, 17 and 18 , and from N-benzylcycloheptindol-1-one 22 were unsuccessful. The preparation of 4,5-dihydro-2-phenyl-1-thienylmethyl-3H-pyridazin-3-one 20 and of the 5-aminopyrazole 21 are reported. 相似文献
995.
V. Jedináková L. Kuča M. Vojtíšková 《Journal of Radioanalytical and Nuclear Chemistry》1980,59(1):125-132
We have investigated the effect of coextraction of lanthanides and yttrium on the distribution coefficients DAm in the extraction of americium by benzyldimethyldodecylammonium nitrate (BDMLNNO3) from nitrate solutions. In the coextraction of lanthanides, the extraction of Am(NO3)3 is suppressed, which is markedly manifested in the extraction of light lanthanides (La, Ce, Pr); of the series of lanthanides their extraction is the highest. The effect of nitric acid and the possibility of separation of lanthanides and americium by the application of three-stage multiple extraction is discussed. 相似文献
996.
Gracia CA Gómez-Barreiro S González-Pérez A Nimo J Rodríguez JR 《Journal of colloid and interface science》2004,276(2):408-413
Static (SLS) and dynamic (DLS) light-scattering techniques were applied to the study of the aggregation of dodecyl- (C12DBACl), tetradecyl- (C14DBACl), and hexadecyldimethylbenzylammonium (C16DBACl) chlorides in water and in 0.01 and 0.05 m NaCl aqueous solutions at 25 degrees C. Results of SLS measurements yielded critical micelle concentration (cmc) values for aqueous and NaCl solutions. The aggregation numbers of the micelles for the homologous surfactants are low but increase with chain length and ionic strength of the solution. Various patterns of changes of the diffusion coefficient, D, as a function of chain length, molality, and with ionic strength were found for the studied surfactants. Transformations in the structure of micelles of C14DBACl in 0.01 m NaCl occur at a concentration of surfactant of about 0.01 m. Such transformations, presumably due to rodlike structure, are the more extensive the higher the concentration of NaCl. The concentration of C16DBACl in 0.05 m NaCl covers the range where already repulsive interactions between micelles occur, as judged by the strongly negative slope of the D versus molality plot. To provide additional information on the suggested transformations, complementary viscosity measurements for C14DBACl in 0.01 m of NaCl have been performed. 相似文献
997.
Arafat A Schroën K de Smet LC Sudhölter EJ Zuilhof H 《Journal of the American Chemical Society》2004,126(28):8600-8601
This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRRAS). Further functionalization was performed by reaction of Si3Nx with a trifluoroethanol ester alkene (CH2=CH-(CH2)8CO2CH2CF3) followed by basic hydrolysis to afford the corresponding carboxylic acid-terminated monolayer with hydrophilic properties. These results show that Si3Nx can be functionalized with a tailor-made organic monolayer, has highly tunable wetting properties, and displays significant potential for further functionalization. 相似文献
998.
Hevia E Pérez J Riera V Miguel D Campomanes P Menéndez MI Sordo TL García-Granda S 《Journal of the American Chemical Society》2003,125(13):3706-3707
As depicted in the scheme, the alkylidenamido complex 1, a N-rhenaimine, reacts with ketenes to afford the beta-lactams 2-4, which possess a {Re(CO)3(bpy)} fragment as substituent at nitrogen. Clean demetalations using HOTf or MeOTf yield the free beta-lactams or N-methyl-beta-lactams along with [Re(OTf)(CO)3(bpy)]. DFT calculations help to rationalize why the reaction is faster than those of non transition metal N-substituted imines. 相似文献
999.
Rodríguez-Cea A de la Campa MR Sanz-Medel A 《Analytical and bioanalytical chemistry》2005,381(2):388-393
Cytochromes P-450 are members of a superfamily of hemoproteins involved in the oxidative metabolism of various physiological and xenobiotic compounds in eukaryotes and prokaryotes. The multiplicity of this group of enzymes has been widely studied by chromatographic techniques, mainly high-performance liquid chromatography (HPLC). Because these enzymes are membrane-bound proteins, sample preparation for chromatographic separation of P-450 enzymes requires a solubilization step. The sample-preparation procedures are critical, because detergents affect not only the efficiency of protein solubilization but also their further chromatographic resolution. Trout liver microsomes have been taken here as a model sample to investigate iron speciation in cytochrome P-450. Trouts were treated intraperitoneally with -naphthoflavone, a potent inducer of some P-450 enzymes, and a microsomal suspension containing 7.4±0.1 nmol mL–1 P-450 enzymes was obtained by ultracentrifugation. Lubrol PX was selected as detergent for solubilization, resulting in about 90% solubilization recovery. The solubilized cytochromes P-450 were further separated by AE–FPLC, with UV detection, or coupled to ICP–MS with an octapole reaction system, ICP–(ORS)MS (monitoring Fe signals at masses 54, 56, and 57). A sampling procedure and chromatographic conditions are developed and were successfully applied to iron speciation in trout liver P-450 enzymes. ICP–(ORS)MS detection of P-450 enzymes is Fe-specific and so will give accurate information on the prosthetic group of the protein, which can constitute an advantageous alternative to classical methods for detection of these hemoproteins. 相似文献
1000.
Fourier-transform infrared (FTIR) spectroscopy has been a major point of development in many wine laboratories in recent years. It enables almost instant analysis of several properties of wine, usually with very good precision and accurate results. Nevertheless, validation procedures should not be forgotten and should be fully performed. Recovery experiments were performed by spiking wine samples with different amounts of organic acids (tartaric, malic, lactic, acetic and citric—the most prominent in wines). After FTIR analysis of the total acidity and of each organic acid concentration, recoveries were calculated. For total acidity recovery results were, in general, good and very close to 100% (64–111%). On the other hand, for individual organic acid concentrations, the recovery results were lower than 100% (11–73%) for all spiking additions. These results could be explained by spectroscopic interferences between the organic acids. Because they have similar infrared spectra, it is not easy to distinguish between them and, therefore, to achieve accurate calibration. When total acidity, with a different infrared spectrum from the other abundant compounds in the wine, was taken as a single property the recovery results were acceptable. 相似文献