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1.
2.
3-Methyl-5-oxo-1-phenyl-2-pyrazolin-4-ylazo-2'-(6',8'-naphthalenedisulfonic acid) (disodium salt) is proposed as a new reagent for the gravimetric determination of zirconium. The precipitate formed at pH 1–1.5 can be weighed directly and there are few interferences. 相似文献
3.
Li W Nelson DP Jensen MS Hoerrner RS Javadi GJ Cai D Larsen RD 《Organic letters》2003,5(25):4835-4837
Imidazo[1,2-a]pyrimidine can be arylated at the 3-position with aryl bromides in the presence of base and a catalytic amount of palladium. This provides an efficient one-step synthesis of 3-arylimidazo[1,2-a]pyrimidines from the unsubstituted heterocycle. [reaction: see text] 相似文献
4.
M. Ştefănescu M. Stoia O. Ştefănescu A. Popa M. Simon C. Ionescu 《Journal of Thermal Analysis and Calorimetry》2007,88(1):19-26
Hybrid organic-inorganic materials,
silica – polyols (ethylene-glycol – EG; 1,2 propane diol –
1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared
by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols,
in acid catalysis. The resulting materials were studied by thermal analysis
(in air and nitrogen), FTIR and solid state 29Si-NMR
spectroscopy. These techniques evidenced the presence of polyols in the silica
matrix both hydrogen bounded and chemically bounded in the silica network.
The thermal analysis proves to be the most appropriate technique to evidence
the organic chains linked in the matrix network and to follow the thermal
evolution of the gels to the SiO2 matrix. 相似文献
5.
It is shown that on the superacid cyclization of esters of bishomobicyclogeranylgeranic and E,E-bishomofarnesic acids fully cyclized hydroxyesters are formed in good yield, while on the interaction of esters of 6-hydroxy- and 6-acyloxy-15-bishomobicyclogeranylgeranic acids with a superacid no carbocyclization takes place. 相似文献
6.
3-Mercapto-2(1H)-pyridinone (1) can be synthesized in three simple high-yielding steps from readily available 2-tert-butylthiazolo[4,5-b]pyridine (2). Its disodium salt condenses with o-chloronitrobenzene, 2-chloro-3-nitropyridine, and 3-chloro-4-nitropyridine 1-oxide to give respectively 4-azaphenoxathiine (10), 1,6-diazaphenoxathiine (12), and 2,6-diazaphenoxathiine 2-oxide (14) which reduces to 2,6-diazaphenoxathiine (15). The structures of these previously unreported azaphenoxathiine systems were confirmed by assignment of their respective (13)C NMR spectra. 相似文献
7.
In this study the influence of the experimental conditions on the obtention of polyelectrolyte multilayer capsules was investigated. Two ways of the simple coacervation method was used to obtain spherical capsules involving chitosan and hyaluronan, chitosan being inside the particle covered by a hyaluronan layer to increase the biocompatibility. The 1H-NMR spectroscopy confirmed a polyelectrolyte complex formation and the optical microscopy shows that the complexed capsules have good sphericity with average diameters ranging from 590 at 1550 μm in the experimental conditions adopted. One can observe that in the acid medium the complexed capsules are much stable than the chitosan beads. The structures described provide a starting point for the design and fabrication of complexed capsules made of two biocompatible natural polymers with potential applicability in medical or pharmaceutical applications. Few diffusion experiments demonstrated that the complexed layer controls the diffusion of dextran included in the chitosan inner domain. 相似文献
8.
D. Humelnicu G. Drochioiu K. Popa 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):291-293
The efficiency of the yeast suspension ofSaccharomyces cerevisiae was studied in the decontamination of radioactive residual waste waters and in the biological behavior of the levuric mass.
The effect of reaction time on the amino acid content in the supernatant and on the concentration of radioactive ions was
also investigated. The reaction of yeast with the toxic agent showed that the living matter behaves differently from the chemical
components of the cell. The yeast had the tendency to aggregate in the presence of radioactive ions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
We show that the kinetic model of a single rate-determining step in a reaction mechanism can be extended to systems with multiple overall reactions for which the elementary reactions obey nonideal or fractal kinetics. The following assumptions are necessary: (1) The system studied is either closed or open, but no constraints exist preventing the evolution toward equilibrium. (2) Elementary reactions occur in pairs of forward and backward steps. (3) The kinetics of the elementary steps are either nonideal or fractal and are compatible with equilibrium thermodynamics. (4) The number of reaction routes is identical with the number of rate-determining steps. If these hypotheses are valid, then the overall reaction rates can be explicitly evaluated: they have a form similar to the kinetic equations for the elementary reactions and the apparent reaction orders and fractal coefficients can be expressed analytically in terms of the kinetic parameters of the elementary reactions. We derive a set of relationships which connect the equilibrium constants of the reaction routes, the corresponding overall rate coefficients, and the stoichiometric numbers of the rate-determining steps. We also derive a set of generalized Boreskov relations among the apparent activation energies of the forward and backward overall processes, the corresponding reaction enthalpies, and the stoichiometric coefficients of the rate-determining steps. If the elementary reactions obey fractal kinetics, the same is true for the rate-determining steps. The fractal exponents of the forward and backward overall reactions are linear combinations of the fractal exponents of the fractal elementary reactions. Similar to the theory of single rate-determining steps, our approach can be used for selecting suitable reaction mechanisms from experimental data. 相似文献
10.
A new polarimetric procedure has been developed for the rapid determination of zirconium in the presence of tartrazin as reagent This determination is possible in the presence of uranium. 相似文献