共查询到20条相似文献,搜索用时 31 毫秒
1.
Rūta Araminaitė Rasa Garjonytė Albertas Malinauskas 《Central European Journal of Chemistry》2009,7(4):739-744
Electrooxidation of ascorbate has been studied with the use of a rotating disk electrode. The results obtained show an efficient
electrocatalytic oxidation of ascorbate at the Prussian blue (PB) modified electrode to proceed in solutions of pH 5.5 and
7.3. Depending on solution pH, the onset potential for ascorbate electrooxidation at PB modified electrode appears shifted
by 0.1–0.2 V to lower values, as compared to an unmodified glassy carbon electrode. Within the electrode potential window
of 0.3 to 0.5 V vs. Ag/AgCl, and electrode rotation velocity of 50–2000 rpm, the catalytic current obeys Koutecky-Levich equation at a submillimolar
ascorbate concentration. Kinetic current densities, obtained from the data treatment, are higher for a pH 5.5 solution, and
also at higher electrode potential.
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2.
Anuţa Câmpean Mihaela Tertiş Robert Săndulescu 《Central European Journal of Chemistry》2011,9(4):688-700
Electrochemical behaviour of some alkaloids, namely: caffeine, aminophylline, theophylline, codeine phosphate and papaverine
hydrochloride, that are in solution in various combinations or in the presence of other compounds contained in pharmaceuticals
or in real samples (urine) was investigated using cyclic voltammetry (CV), square-wave voltammetry (SWV) and differential
pulse voltammetry (DPV) on electrochemically activated glassy carbon electrode.
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3.
Phase equilibria established in the PbO - BiVO4 system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed
using DTA and XRD.
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4.
Santosh S. Katkar Pravinkumar H. Mohite Lakshman S. Gadekar Balasaheb R. Arbad Machhindra K. Lande 《Central European Journal of Chemistry》2010,8(2):320-325
A rapid and an efficient one-pot method for the synthesis of quinoxalines catalysed by ZnO-beta zeolite at room temperature
is described. This environmentally benign method provides several advantages over methods that are currently employed such
as a simple work-up, mild reaction conditions, good to excellent yields, and a process to recover and reuse the catalyst for
several cycles with consistent activity.
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5.
Vivek Srivastava 《Central European Journal of Chemistry》2010,8(2):269-272
Sulphonimide based organocatalyst was used to catalyze the aldol reaction in ionic liquid media. On the basis of yield and
selectivity the ionic liquid mediated system was found superior in comparison with organic solvents. The added advantages
of this ionic liquid mediated organocatalysis are easy recovery of product and the recyclability of the organocatalyst.
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6.
Nitin A. Mirgane Sandip B. Kotwal Anil V. Karnik 《Central European Journal of Chemistry》2010,8(2):356-360
Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]+[Cl]−, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room
temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.
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7.
Zehra Durmus Hüseyin Kavas Abdulhadi Baykal Muhammet S. Toprak 《Central European Journal of Chemistry》2009,7(3):555-559
A novel environmental friendly, room temperature route using an ionic liquid 1-n-butyl-3-methylimidazolium hydroxide ([BMIM]OH)
for the synthesis of Mn3O4 nanoparticles is presented. The product was characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction,
and transmission electron microscopy. Phase purity was confirmed by XRD, and X-ray line profile fitting determined a crystallite
size of 42 ± 11 nm. TEM analysis revealed various morphologies. EPR measurements have indicated the existence of long-range
interactions, due to the wide range of particle sizes and morphologies observed.
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8.
Lakshman S. Gadekar Shivshankar R. Mane Santosh S. Katkar Balasaheb R. Arbad Machhindra K. Lande 《Central European Journal of Chemistry》2009,7(3):550-554
Natural scolecite has been found as an effective catalyst for the one-pot synthesis of 2,4,5-triarylimidazole derivatives
via a three component reaction using benzil or benzoin, aldehydes and ammonium acetate. This method provides several advantages
such as being environmentally benign, reusable, possessing high yields with increased variations of the substituents in the
product and preparative simplicity.
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9.
A novel hydroxyamino phosphane was synthesised through the reaction of 2-imidazolidinone with ClPPh2 and subsequently reaction
of the resulting bisphosphino derivative with the Grignard reagent BrMgC5H11. The interaction of the pentyl substituent with one of the two phosphino groups and the structure in solution is shown by
multinuclear NMR-spectroscopy..
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10.
11.
Tuula Kylmälä Jan Tois Youjun Xu Robert Franzén 《Central European Journal of Chemistry》2009,7(4):818-826
Diflunisal and Felbinac, two FDA-approved NSAIDs and other biphenyl carboxylic acids were prepared in one step by a simple
and clean Suzuki cross-coupling reaction using an easily synthesized, air and moisture stable, palladium-diamine complex.
The yield (93%) for the one-step preparation of Diflunisal is the best reported without using a glovebox and a phoshine-based
catalyst.
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12.
The oxidation processes of 2,6-diisopropylnaphthalene and 4,4′-diisopropylbiphenyl with oxygen in the presence of a catalyst,
composed of copper(II) chloride and tetrabutylammonium bromide, were investigated. It was found that, in essence, only one
isopropyl group undergoes oxidation, and obtained mixtures contained mainly peroxide, alcohol, ketone and only small amounts
of hydroperoxide.
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13.
The electrochemical reduction of four arylidene substituted derivatives of dibenz-[b,e]-thiepin-5,5-dioxide-11- one has been
studied by cyclic voltammetry on platinum (Pt) electrode in aprotic media (DMSO), coupled with spectral EPR techniques. From
the analysis of cyclic voltammetry experiments, aided by digital simulations using DigiSim software, the kinetic and thermodynamic
parameters were evaluated for each system. The electrochemical behaviour is strongly directed by the nature of the arylidene
substituents bound to the central heterocycle. The electrochemical investigation and solvent dependent semiempirical modeling
using the PM3 hamiltonian in the frame of AMPAC program package allowed a rationalisation of experimental data regarding the
electrochemical reduction and the reactivity of the intermediate species involved.
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14.
Morteza Bahram Khalil Farhadi Farzin Arjmand 《Central European Journal of Chemistry》2009,7(3):524-531
A new differential pulse voltammetric method for dopamine determination at a bare glassy carbon electrode has been developed.
Dopamine, ascorbic acid (AA) and uric acid (UA) usually coexist in physiological samples. Because AA and UA can be oxidized
at potentials close to that of DA it is difficult to determine dopamine electrochemically, although resolution can be achieved
using modified electrodes. Additionally, oxidized dopamine mediates AA oxidation and the electrode surface can be easily fouled
by the AA oxidation product. In this work a chemometrics strategy, partial least squares (PLS) regression, has been applied
to determine dopamine in the presence of AA and UA without electrode modification. The method is based on the electrooxidation
of dopamine at a glassy carbon electrode in pH 7 phosphate buffer. The dopamine calibration curve was linear over the range
of 1–313 μM and the limit of detection was 0.25 μM. The relative standard error (RSE %) was 5.28%. The method has been successfully
applied to the measurement of dopamine in human plasma and urine.
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15.
Ghasem Rezanejade Bardajee Farnaz Jafarpour Hamid Samareh Afsari 《Central European Journal of Chemistry》2010,8(2):370-374
In this report, a rapid, efficient and environmental friendly synthesis of 3-carboxycoumarins under ultrasound irradiation
in water media is described. The Knoevenagel condensation of Meldrum’s acid with substituted benzaldehydes in the presence
of zirconium oxide chloride (ZrOCl2·8H2O) and ultrasonic irradiation in water gave the corresponding 3-carboxycoumarins in good to excellent yields.
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16.
Eugenia D. Teodor Simona C. Liţescu Antonela Neacşu Georgiana Truică Camelia Albu 《Central European Journal of Chemistry》2009,7(3):560-568
The study aims to establish several definite criteria which will differentiate Romanian amber and Baltic amber to certify
the local or Baltic origin of the materials found in archaeological sites on the Romanian territory, by using light microscopy
and performing analytical methods, such as Fourier transform infrared spectroscopy-variable angle reflectance and liquid chromatography
with mass spectrometry detection. Experiments especially by Fourier transformed infrared spectroscopy, were applied to a wide
range of samples with controlled origin. The methods were optimised and resulted in premises to apply the techniques to analysis
of the archaeological material.
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17.
Francis E. Appoh Marcy J. Manning Teri J. Gullon Margaret A. Hansen Emily C. Bevans Krista D. M. Hogan Courtney S. Turner Christopher M. Vogels Andreas Decken Stephen A. Westcott 《Central European Journal of Chemistry》2008,6(3):359-364
The Ugi reaction with formylphenylboronic acid derivatives as the carbonyl component proceeds to give the corresponding boron-containing
dipeptide derivatives (Ugi products) in good yields.
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18.
Renata Farkas Mercedesz Törincsi Pal Kolonits Jenö Fekete Oscar Jimenez Alonso Lajos Novak 《Central European Journal of Chemistry》2010,8(2):300-307
During the diazo-coupling reaction, nucleophilic displacement of a nitro group was also observed. This was the main reaction
(1→7) when the starting amine bore either a chlorine or methoxy group at the para position (1b–c). The newly prepared compounds (7) might serve as convenient building blocks in synthesis of some heterocycles.
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19.
Iwona Binkowska Włodzimierz Gałęzowski Arnold Jarczewski 《Central European Journal of Chemistry》2010,8(3):582-586
Proton transfer reactions rates between carbon acids 1-nitro-1-(4-nitrophenyl)ethane (NPNE), 2-methyl-1-nitro-1-(4-nitrophenyl)propane
(MNPNP)) and phosphazenes (BEMP, BTPP, P1-t-Oct) in tetrahydrofuran have been measured, and the activation parameters were determined. The results are compared with
those previously obtained for P1-t-Bu phosphazene, guanidines and amidines.
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20.
Octavian Staicu Domnina Razus Valentin Munteanu Dumitru Oancea 《Central European Journal of Chemistry》2009,7(3):478-485
The heterogeneous catalytic ignition of lean to stoichiometric n-butane/air mixtures were studied at various total pressures
between 10 and 100 kPa and at temperatures equal to or larger than the critical ignition temperatures. The induction periods,
ignition and extinction temperatures were measured under strict isothermal conditions. The discussion presented in this paper
is based on several literature models. The data analysis allowed for the determination of the overall kinetic parameters.
The rigorous isothermal conditions indicated that the extinction temperatures are lower than the ignition, a behavior different
from the results obtained in stagnation-point flow reactors.
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