共查询到20条相似文献,搜索用时 62 毫秒
1.
Andris Zicmanis Galina Vavilina Svetlana Drozdova Peteris Mekss Maris Klavins 《Central European Journal of Chemistry》2007,5(1):156-168
Alkylation of indole salts in different ionic liquids is reported. Ionic liquids increase the alkylation reaction rate of
ambident indole anion and reduce the effects of counter ions and/or additives, the alkylation reaction rates being independent
of the presence of small amounts of protic solvents or water.
相似文献
2.
The geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo
and 5,7-dinitro derivatives were obtained by the density functional theory (DFT) calculations with Becke3-Lee-Parr (B3LYP)
functional and 6-31G* basis set. The effects of chloride, bromide, iodide and nitro substituent on the vibrational frequencies
of 8-hydroxyquinoline have been investigated. The assignments have been proposed with aid of the results of normal coordinate
analysis. The observed and calculated spectra are found to be in good agreement.
相似文献
3.
A palladium complex with an aminophosphine ligand has been prepared and investigated as a catalyst precursor in Suzuki coupling
reactions in toluene. Nanoparticles composed of elemental palladium have been isolated from the reaction media and analyzed
using transmission electroscopic microscope (TEM), which shows the essential catalysts palladium nanoparticles to have a size
of ca. 3.0 nm.
dedicate to the 60th birthday of Prof. Dr. Yuan Kou 相似文献
4.
Paraskevas D. Tzanavaras Demetrius G. Themelis Fotini S. Kika 《Central European Journal of Chemistry》2007,5(1):1-12
The present study reviews more than twenty years (1985-present) of published research on the development and application of
analytical procedures for the determination of chlorine dioxide, a widely used disinfectant and bleaching agent. The review
covers a variety of techniques including batch and automated spectrophotometry and fluorimetry, electroanalysis and chromatography.
The analytical figures of merit to the methods are presented, while critical discussion regarding their advantages and disadvantages
is addressed.
相似文献
5.
Ksenija R. Kumrić Tatjana M. Trtić-Petrović Ljubiša M. Ignjatović Jožef J. Čomor 《Central European Journal of Chemistry》2008,6(1):65-69
Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA.
Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically,
resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL−1 lutetium could be detected after a 2 min deposition.
相似文献
6.
Abdülhadi Baykal Yüksel Köseoğlu Mehmet Şenel 《Central European Journal of Chemistry》2007,5(1):169-176
Heating hydrous manganese (II) hydroxide gel at 85 °C for 12 hours produces Mn3O4 nanoparticles. They were characterized by X-ray powder diffraction (XRD) and infrared spectroscopy (FTIR). The particle size
estimated from the SEM and X-ray peak broadening is approximately 32 nm, showing them to be nanocrystalline. EPR measurements
confirm a typical Mn2+signal with a highly resolved hyperfine structure.
相似文献
7.
Surface analysis of the size-fractioned urban aerosols by secondary ion mass spectrometry (ToF-SIMS)
The secondary ion mass spectrometry method (ToF-SIMS) has been applied to the analysis of some mineral and organic species
on the surface layers of airborne urban particulates. Particulate matter was collected on aluminum sheets of the 8-stage Anderson
type cascade impactor from three different sampling sites in the city of Lodz, Poland, which were different in terms of aerosol
source apportionment. The obtained results show that vehicle combustion products occur mainly in fine fraction with aerodynamic
diameters below 1μm. The main contribution to the mineral components comes from direct and traffic related soil resuspension.
相似文献
8.
In this study, a series of new 5-phenylazo-6-aminouracil dyes were prepared by linking m-,p-nitroaniline, m-,p-chloroaniline,
m-,p-anisidine, m-,p-toluidine, m-,p-cyanoaniline, p-ethoxyaniline, p-phenoxyaniline, p-ethylaniline, p-acetamidoaniline,
p-acetylaniline, p-carboxyaniline and aniline to 6-aminouracil. The prepared dyes were characterized by UV-vis, FT-IR, 1H NMR spectroscopic techniques and elemental analysis. The effect of acid and base upon the UV-vis spectra of these dyes were
investigated. In addition, the solvatochromic behaviors and substituent effects in various solvents were evaluated.
相似文献
9.
Adina Raducan Alexandra Olteanu Mihaela Puiu Dumitru Oancea 《Central European Journal of Chemistry》2008,6(1):89-92
The kinetics of the reaction between malachite green (MG) and sodium hydroxide (MG fading) was studied using a spectrophotometric
method in the presence of two cationic surfactants, cetyl-benzyl-dimethyl-ammonium chloride (CBDAC) and hexadecyl-trimethylammonium
bromide (HTAB) and one anionic surfactant, sodium dodecyl sulphate (SDS) at concentrations below and above critical micellar
concentrations. The cationic surfactants have a catalytic effect, while the anionic surfactant has an inhibitory effect on
the reaction. A kinetic model describing the influence of surfactant on reaction rate was developed. The results are discussed
on the basis of electrostatic and hydrophobic interactions between the kinetic micelles and malachite green.
相似文献
10.
Agata Siwek Monika Wujec Maria Dobosz Ewa Jagiełło-Wójtowicz Anna Chodkowska Agnieszka Kleinrok Piotr Paneth 《Central European Journal of Chemistry》2008,6(1):47-53
By the reaction of 2-methyl-furan-3-carboxylic acid hydrazide with isothiocyanates, 1-[(2-methyl-furan-3-yl)carbonyl]-4-substituted
thiosemicarbazides 1 were obtained. Further cyclization with 2% NaOH led to the formation of 3-(2-methyl-furan-3-yl)-4-substituted-Δ2-1,2,4-triazoline-5-thiones 2. The pharmacological effects of 2 on the central nervous system in mice were investigated. Strong antinociceptive properties
of the investigated derivatives were observed in a wide range of doses.
相似文献
11.
A strange effect was observed while using the method of quasi-simultaneous determination of electrochemical voltage noise
and impedance to obtain information on the kinetics of the hydrogen evolution reaction on Ag and Cu microelectrodes. Beyond
a certain polarizing current density we found microvolt-amplitude potential oscillations on both electrodes with a frequency
in the 5 Hz–5 kHz range. The oscillations were observed in every single experiment with Ag and Cu, while no oscillatory behavior
was observed during the control experiments with the Pt microelectrode. The presence of the oscillations indicates that the
mechanism of hydrogen evolution is more complex compared to the original assumption.
相似文献
12.
Yuhai Sun Yujun Feng Hongwei Dong Zhi Chen Likun Han 《Central European Journal of Chemistry》2007,5(2):620-634
A series of homologous gemini surfactants possessing identical hydrophobic chains but different ionic head groups (cationic,
anionic, zwitterionic) were synthesized, and their aqueous solution properties were examined. The results showed that the
surface activities of gemini surfactants are superior to those of corresponding conventional monomeric surfactants, and molecular
arrangements of gemini surfactants at the air-water interface are tighter than those of corresponding conventional surfactants.
It was also found that zwitterionic gemini surfactant possesses the highest surface activity among the three surfactants.
The behavior at the air-water interface is closely related to the molecular structural features of surfactants, which provide
an indication for synthesizing highly-efficient surfactants.
相似文献
13.
The determination of paeoniforin, paeonol, and censenoside Rg1 in traditional Chinese medicinal preparations, Tze Po San Pien pills and Liuwen Dihuang pills has been investigated by micellar
electrokinetic capillary electrophoresis with borate buffer (20 mM), sodium dodecylsulfate (30 mM) and acetonitrile (20%)
as background electrolytes (pH 9.30), 20 kV applied voltage and 203 nm UV detection. The effects of SDS concentration, borate,
buffer pH, and organic modifier on electrophoretic behavior and separation are discussed. Regression equations revealed linear
relationships between the peak-area of each component and the content with the correlation coefficients from 0.9982 to 0.9999.
In addition, the levels of the active compounds in two kinds of traditional Chinese medicinal preparations were easily determined
with the recoveries from 93.1% to 108.2%.
相似文献
14.
A simple and convenient method for the preparation of needle-shape nanoparticles of β-Ni(OH)2 has been developed. Results show that a needle-shaped β-Ni(OH)2 can be easily obtained in the presence of ethylenediamine and sodium dodecylbenzene sulfonate within a size from 100 to 200
nm. The shape and structure of the product were characterized by XRD, TEM and FT-IR. It is noteworthy that the formation of
needle-shape β-Ni(OH)2 benefits from the addition of sodium dodecylbenzene sulfonate. The optimum preparation conditions and the possible mechanism
are also discussed.
相似文献
15.
16.
Li-hua Yu Shou-min Zhang Xianzhi Guo Da Wang Shu-rong Wang Shi-hua Wu 《Central European Journal of Chemistry》2007,5(1):144-155
The Co-Pd/SiO2 and Co-Cu/SiO2 catalysts were prepared via solvated metal atom impregnation (SMAI) method and investigated for the Fischer-Tropsch (F-T)
synthesis. The catalysts contained 5wt.% Co and a weight ratio of Pd (or Cu) to Co of 1/30. XPS indicated that Co, Pd and
Cu were in metallic state. The results of XPS and magnetic measurements showed that Co and Pd (Cu) were alloyed. The Co particles
on the catalysts were very highly dispersed and they displayed superparamagnetic behavior. FT-IR indicated that the electrons
shifted from Cu and Pd to Co. Catalytic tests showed that CO hydrogenation rates followed the order Pd-Co > Cu-Co > Co.
相似文献
17.
Maria M. Milanova Dimitar S. Todorovsky Christo C. Balarew Natalia L. Minkova Katya I. Ivanova 《Central European Journal of Chemistry》2007,5(1):13-19
The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO
4
+
in determining the composition of the equilibrium phases is revealed.
相似文献
18.
This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations
in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding
the measurements’ results were identified as contributions to linear least — square or weighted regression lines, precision,
trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure,
especially the amount of nitrate in waste and potable waters.
The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement
uncertainties determined by the two methods, the weighted and linear least — square methods, is negligible.
相似文献
19.
A procedure for direct electrochemical deposition of polyaniline-polypyrrole blend coating on the surface of stainless steel
wire was suggested. Incorporation of polyaniline and polypyrrole into the blend coating was confirmed by infrared spectroscopy.
Key parameters (pyrrole, aniline, dopant and sulphuric acid concentrations and deposition potential) influencing the coating’s
mechanical stability and surface homogeneity were optimised and thermostability of the coating was investigated. A possibility
to apply the coating as a new fibre for solid phase microextraction was demonstrated. The coating showed better selectivity
toward aromatic, hydrophobic compounds.
相似文献
20.
Li-Wen Xu Ming-Song Yang Jian-Xiong Jiang Hua-Yu Qiu Guo-Qiao Lai 《Central European Journal of Chemistry》2007,5(4):1073-1083
Ionic liquid-functionalized mesoporous materials exhibited high catalytic activity in versatile organic reactions, such as
cycloaddition of carbon dioxide (CO2) with epoxide, aza-Michael addition of amines to α, β-unsaturated carbonyl compounds, and the Biginelli reaction of aldehyde, ethyl acetoacetate and urea. Recycling of the catalyst
in these reactions could be carried out and the catalyst used at least five times without significant loss in activity.
相似文献