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71.
On reaction with organolithium reagents followed by hydrolysis and distillation, N-vinylpyrrolidone ( 1 ) gives five-membered ring imines 3-8 , whereas N-vinylcaprolactam ( 2 ) gives mixtures of seven-membered ring imines and the corresponding ∈-amino ketones. 相似文献
72.
Micha Kijak Anna Zieli ska Charles Chamchoumis Jerzy Herbich Randolph P. Thummel Jacek Waluk 《Chemical physics letters》2004,400(4-6):279-285
Depending on the polarity and protic abilities of the solvent, 2-(2′-pyridyl)pyrrole can exist in either syn or anti rotameric forms. In nonpolar solvents, intramolecular excited state single proton transfer is observed, manifested by the appearance of low-energy tautomeric emission. The solvent-assisted excited state double proton transfer reaction is also detected. DFT calculations confirm low barriers for both single and double proton transfer processes in the lowest excited singlet state and show different character of the tautomerization in both cases: in the intramolecular reaction, mutual approach of two nitrogen atoms plays an important role. 相似文献
73.
The asymmetric direct aldol condensation of aldehydes with ethyl- and propylketones is catalyzed by syn-alpha-aminoalcohol-Yb(OTf)3 complexes, yielding the anti-1,3-diol monoesters with high diastereocontrol and good enantioselectivity. Three adjacent stereogenic centers are created in a simultaneous aldol condensation and Evans-Tishchenko reduction in an acyclic system. 相似文献
74.
Andrzej Małecki Jalees A.K. Tareen Jean Pierre Doumerc Louis Rabardel Jean Claude Launay 《Journal of solid state chemistry》1985,56(1):49-57
Kinetics of thermal decomposition in vacuum of Co3O4 powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co3O4 proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)2/3 = ktn where the activation energy varies with the degree of decomposition. 相似文献
75.
Przychodzeń P Lewiński K Bałanda M Pełka R Rams M Wasiutyński T Guyard-Duhayon C Sieklucka B 《Inorganic chemistry》2004,43(9):2967-2974
The syntheses, X-ray structures, and magnetic behaviors of two new cyano-bridged assemblies, the molecular [Mn(III)(salen)H2O]3[W(V)(CN)8].H2O (1) and one-dimensional [Mn(salen)(H2O)2]2[[Mn(salen)(H2O)][Mn(salen)]2[Mo(CN)(8)]].0.5ClO4.0.5OH.4.5H2O (2), are presented. Compound 1 crystallizes in the monoclinic system, has space group P2(1)/c, and has unit cell constants a = 13.7210(2) A, b = 20.6840(4) A, c = 20.6370(2) A, and Z = 4. Compound 2 crystallizes in the triclinic system, has space group P, and has unit cell dimensions a = 18.428(4) A, b = 18.521(3) A, c = 18.567(4) A, and Z = 2. The structure of 1 consists of the asymmetric V-shaped Mn-NC-W-NC-Mn-O(phenolate)-Mn molecules, where W(V) coordinates with [Mn(salen)H2O] and singly phenolate-bridged [Mn(salen)H2O]2 moieties through the neighboring cyano bridges. The [W(V)(CN)8]3- ion displays distorted square-antiprism geometry. The structure of 2 consists of the cyano-bridged [Mn3(III)Mo(IV)]n- repeating units linked by double phenolate bridges into one-dimensional zigzag chains. The Mn(III) centers are bound to Mo(IV) of square-antiprism geometry through the neighboring cyano bridges. The magnetic studies of 1 reveal the antiferromagnetic intramolecular interactions through the CN and phenolate bridges and the relatively weak intermolecular interactions. Compound 1 becomes antiferromagnetically ordered below TN = 4.6 K. The presence of the magnetic anisotropy is documented with the MH measurements carried out for both polycrystalline and single-crystal samples. At T = 1.9 K, the spin-flop transition is observed in the field of 18 kOe applied parallel to the bc plane, which is the easy plane of magnetization. Field dependence of magnetization of 1 shows field-induced metamagnetic behavior from the antiferromagnetic ground state of ST = 3/2 to the state of ST = 5/2. The magnetic properties of 2 indicate a weak antiferromagnetic interaction between Mn(III) centers in double-phenolate-bridged [Mn(III)(salen)]2 dinuclear subunits and a very weak ferromagnetic interaction between them through the diamagnetic [Mo(IV)(CN)8]4- spacer. 相似文献
76.
The preconcentration and separation of palladium and iridium from base metals is studied with cellulose (Cellex T) and styrene-divinylbenzene (Varion AT 400) anion exchangers. In spite of lower capacity of Cellex T to chloride complexes of Pd and Ir, it allowed to get a higher preconcentration factor. Yields of 92–99% are achieved for Pd and 96–97% for Ir from the solutions containing great excess of base and heavy metals. Graphite furnace atomic absorption spectrometry is used for the final measurements. The procedure has been applied to the determination of palladium in natural samples. 相似文献
77.
Robert Pietrzak Mieczysław Kozłowski Helena Wachowska Jan Yperman 《Central European Journal of Chemistry》2004,2(2):278-289
Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification
and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses
are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy
(FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from
the reaction with HNO3 contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised
by an increased content of organic sulphur species. 相似文献
78.
The desorption of 1,2-dichloroethane from a bed of DTO activated carbon after adsorption from aqueous solution has been investigated. The desorption process was carried out using steam. The basic characteristics of the process were determined. The studies were performed in the temperature range 100-160 degrees C. A steam consumption indicator reduces with an increase of temperature from 100 to 140 degrees C. An elevation of temperature above 140 degrees C does not cause an improvement in the desorption efficiency. The number of performed cycles does not reduce the adsorption capacity of used activated carbon. Studies on the regeneration of the bed saturated with a seven-component mixture of chloroorganic compounds at temperature of 140 degrees C were carried out. The degree of removal of the sum of chloro-derivatives exceeded 0.96 at a volume ratio of steam (recalculated on the condensate) to bed of about 10. It was found that the dechlorination proceeds during desorption at elevated temperature. The quantitative ratio of chloro-derivatives in the desorbate was changed in comparison to the composition of wastewater directed to the adsorption. 相似文献
79.
A new, highly sensitive, fast responding and stable potentiometric biosensor for creatinine determination is developed. The biosensor is based on an ammonium ion-selective electrode. Creatinine deiminase (EC 3.5.4.21) is chemically immobilized on the surface of the polymeric ion-sensitive membrane in the form of monomolecular layer using a simple, one-step carbodiimide covalent attachment method. The resulting enzyme electrodes are useful for measurement under flow injection analysis (FIA) conditions. The biosensors exhibit excellent operational and storage stability. The enzyme electrodes retain over 70% of initial sensitivity after ten weeks of work under FIA conditions. The storage stability at 4 °C is longer than half a year without loss of sensitivity. Under optimized conditions near 30 samples per hour can be analyzed and the determination range (0.02-20.0 mmol l−1) fully covers creatinine concentrations important from clinical and biomedical point of view. The simple biosensor/FIA system has been successfully used for determination of creatinine in urine, serum and posthemodialysate samples. 相似文献
80.
Calorimetry has been used in the investigations of calcium aluminate materials produced as a binder for aluminate-corundum
composites of high refractoriness. The kinetics and of hydration process was thus characterized and the optimum compositions
of initial binders and cement-corundum refractory filler blends could be selected for further tests. The acceleration of heat
evolution - the shortening of so-called induction period and relatively high heat output in the presence of corundum was observed.
It means the acceleration of hydration process, that is early crystallisation of hydration products and subsequent further
dissolution of initial anhydrous aluminate phases. In the presence of fine grained corundum particles these phenomena should
be attributed to the nucleating effect of fine corundum particles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献