Open Access Published by De Gruyter Open Access

Volume 3 Issue 2

June 2005

Issue of Open Chemistry

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Journal Overview

Open Access June 1, 2005

Kinetics of electrode reaction coupled to ion transfer across the liquid/liquid interface

Šebojka Komorsky-Lovrić, Milivoj Lovrić

Page range: 216-229

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Abstract

In the theoretical model it is assumed that a graphite disk electrode is covered by a thin film of solution of decamethylferrocene (dmfc) and some electrolyte CX in nitrobenzene and immersed in an aqueous solution of the electrolyte MX. Oxidation of dmfc is accompanied by the transfer of anion X − from water into nitrobenzene since it is also assumed that cations dmfc + and C + are insoluble in water and cation M + is insoluble in nitrobenzene. Kinetic parameters of the electrode reaction can be determined if the total potential difference across the nitrobenzene/water interface is maintained constant by adding the electrolytes CX and MX in concentrations which are much higher than the initial concentration of dmfc in nitrobenzene.

Open Access June 1, 2005

The ring opening and oligomerisation reactions of an epoxide and an episulfide on aluminosilicates in the liquid phase

András Fási, István Pálinkó, Ágnes Gömöry, Imre Kiricsi

Page range: 230-244

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Abstract

The ring opening reactions of propylene oxide (methyloxirane) or ethylene sulfide )thiirane) were studied in the liquid phase over HZSM-5, HY-FAU or AlMCM-41 at 363 K or 423 K and under 1 or 20 bar pressure in a batch reactor. The proportion of these routes were identified: (i) single C−O scission providing non-cyclic products, (ii) double C−O cleavage leading to the loss of the heteroatom, (iii) oligomerisation resulting in cyclic dimers and the trimer of thiirane and a non-cyclic dimer of methyloxirane. The reaction pathway depended on the conditions and the solid acids used. Findings are compared to those in the gas phase over the same solid acids. Transformation mechanisms are also suggested.

Open Access June 1, 2005

2H Chemical-shift resolution and dipolar2H-1H,2H-15N correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems

Martin Schulz-Dobrick, Ingo Schnell

Page range: 245-251

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Abstract

In solid-state NMR, deuteron (2H) spectroscopy can be performed in full analogy to1H spectroscopy, including2H chemical-shift resolution and2H-X dipolar correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle spinning. Here, 2H-X NMR experiments of this type, including2H-15N and2H-1H chemical-shift correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic protons can readily be replaced by deuterons by recrystallization from D2O. In this way,2H NMR spectroscopy provides information complementary to1H NMR data, which is particularly useful for studying hydrogen bonds in supra- or biomolecular systems.

Open Access June 1, 2005

Determination of gold, palladium and copper by flame atomic absorption spectrometry after preconcentration on silica gel modified with 3-(2-aminoethylamino)propyl group

Mustafa Imamoglu, Ali Aydin, Mustafa Dundar

Page range: 252-262

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Abstract

A preconcentration method of gold, palladium and copper based on the sorption of Au (III), Pd (II) and Cu (II) ions on a column packed with 3-(2-aminoethylamino)propyl bonded silica gel is described. The modified silica gel was synthesized and characterized by FT-IR and C, H, N elemental analysis. At column preconcentration, the effects of parameters such as pH, volume, flow rate, matrix constituents of solutions and type of eluent on preconcentration of gold, palladium and copper were studied. The recoveries of Au (III), Pd (II) and Cu (II) were 98.93±0.51, 98.81±0.36 and 99.21±0.42 % at 95 % confidence level, respectively. The detection limits (δ) of the elements were 0.032, 0.016 and 0.012 μg ml−1, respectively. The preconcentration method was applied for determination of gold and palladium in certified reference material SARM 7B and copper in river and synthetic seawater by FAAS. Gold, palladium and copper were determined with relative error lower than 10 %.

Open Access June 1, 2005

Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO3 and La1−xCaxMnO3

Nikolina Petrova, Dimitar Todorovsky, Veselinka Vasileva

Page range: 263-278

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Abstract

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn3O4 (hausmannite) and LaMnO3 respectively. Parasitic phase(s) are observed in LaxCa1−xMnyO3, produced from LaCaMn-citrate.

Open Access June 1, 2005

Study of catalase immobilized on a silicate matrix for non-aqueous biocatalysis

Elena Horozova, Nina Dimcheva

Page range: 279-287

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Abstract

Catalytic activity of catalase (CAT) immobilized on a modified silicate matrix to mediate decomposition of meta-chloroperoxibenzoic acid (3-CPBA) in acetonitrile has been investigated by means of quantitative UV-spectrophotometry. Under the selected experimental conditions, the kinetic parameters: the apparent Michaelis constat (KM), the apparent maximum rate of enzymatic reaction (Vmaxapp), the first order specific rate constants (ksp), the energy of activation (Ea) and the pre-exponential factor of the Arrhenius equation (Z0) were calculated. Conclusions regarding the rate-limiting step of the overall catalytic process were drawn from the calculated values of the Gibbs energy of activation ΔG*, the enthalpy of activation ΔH*, and the entropy of activation ΔS*.

Open Access June 1, 2005

Parallel synthesis of novel benzimidazoles on a soluble polymer support

Ling-Ju Chang, Manohar Kulkarni, Chung-Ming Sun

Page range: 288-294

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Abstract

Liquid phase combinatorial synthesis using a soluble polyethylene glycol (PEG) polymer support and commercially available 3-nitro-4-fluoro benzoic acid is carried out in order to create a molecular library of trisubstituted benzimidazoles. The PEG-ester conjugate of 3-nitro-4-fluoro benzoic acid is subjected to ipso-fluoro displacement by various primary amines. The nitro group is reduced under neutral conditions using excess zinc and ammonium chloride, producing the polymer-boundo-phenylene diamines. Reaction of the diamines with different aldehydes results in cyclisation to benzimidazoles. The polymer support is cleaved releasing the desired products in high yields and purity. All reactions are performed at room temperature.

Open Access June 1, 2005

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Maria Stoyanova, Stoyanka Christoskova

Page range: 295-310

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Abstract

Catalytic activity of mixed Ni−Fe oxide systems with respect to air oxidation of aqueous cyanide solution at 308 K was investigated. The catalysts employed were prepared by an oxidation-precipitation method at room temperature and were characterized by powder X-ray diffraction (XRD), Mössbauer spectroscopy, and chemical analysis. The cyanide oxidation rate was found to be dependent on the catalyst's calcination temperature, pH of the medium, and catalyst loading. Results revealed that the catalyst calcined at 120°C is the most active where up to 90% of free cyanide (4 mM) was removed after oxidation for 30 minutes in the presence of 2.5 g/L catalyst at pH 9.5. The cyanide conversion becomes less favorable as the pH of the solution increases (with other constant parameters). The selectivity data showed that carbon dioxide is the main oxidation product, regardless of pH of the solution.

Open Access June 1, 2005

2-[3-(Trifluoromethyl)phenyl]furo[3,2-b]pyrroles: synthesis and reactions

Peter Gajdoš, Soňa Pavlíková, Filip Bureš, Alžbeta Krutošíková

Page range: 311-325

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Abstract

The synthesis and reactions of methyl 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole-5-carboxylate (1a) are described. Upon reaction with methyl iodide, benzyl chloride, or acetic anhydride, this compound gave N-substituted products 1b-d. By hydrolysis of compounds 1a-c, the corresponding acids 2a-c were formed, or by reaction with hydrazine-hydrate, the corresponding carbohydrazides 3a-c were formed. By heating 2-[3-(trifluoromethyl)phenly]-4H-furo[3,2-b]pyrrole-5-carboxylic acid (2a) in acetic anhydride, 4-acetyl-2-[3-(trifluoromethyl)phenyl]furo[3,2-b]pyrrole (4) was formed. By hydrolysis of 4, 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole (5a) was formed, and reactions with methyl iodide or benzyl chloride gave N-substituted products 5b-c. The reaction of 4 with dimethyl butynedioate gave substituted benzo[b]furan 6. Compound 3a reacted with triethyl orthoesters giving 7a-c, which afforded with phosphorus (V) sulphide the corresponding thiones 8a-c. The thiones 8a-c reacted with hydrazine hydrate to form hydrazine derivatives 9a-c. The reaction of triethyl orthoformiate with compounds 9a-c led to furo[2′,3′: 4,5]pyrrolo[1,2-d][1,2,4]triazolo[3,4-f][1,2,4]triazines 10a-c. Hydrazones 11a-c were formed from 3a-c and 5-[3-(trifluoromethyl)phenyl]furan-2-carboxaldehyde. The effect of microwave irradiation on some condensation reactions was compared with “classical” conditions. The results showed that microwave irradiation shortens the reaction time while affording comparable yields.

Open Access June 1, 2005

Oxidation of some catecholamines by sodium N-chloro-p-toluenesulfonamide in acid medium: A kinetic and mechanistic approach

Puttaswamy, R. Jagadeesh, Nirmala Vaz

Page range: 326-346

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Abstract

The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine (E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]o, fractional-order in [substrate]o, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed and the derived rate law are consistent with the observed kinetics.

Open Access June 1, 2005

Kinetic study of adsorption of some biocompounds at the oil/water interface

Gheorghe Tomoaia, Andrada Tomoaia-Cotisel, Maria Tomoaia-Cotisel, Aurora Mocanu

Page range: 347-360

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Abstract

The adsorption kinetics of some local anesthetics, like dibucaine and tetracaine, and of stearic acid from bulk solutions at the oil/water interface was studied by using the pendent drop and ring methods. The anesthetics were dissolved in aqueous solutions (pH 2), and the fatty acid was dissolved in benzene, each biocompound at several different concentrations in bulk solutions. Kinetic equations for Langmuir mechanism of adsorption at oil/water interface were tested. The kinetic analysis shows that Langmuir kinetic approach describes the dynamic interfacial pressures within the limits of the experimental errors over a wide range of time and for different surfactant concentrations in bulk solutions. It is also concluded that this approach allows the calculation of the ratio of the adsorption and desorption rate constants of these biocompounds at the oil/water interface. Obtained results are in substantial agreement with earlier reported data for the surfactant adsorption as, well as with their molecular structure.

Open Access June 1, 2005

Density functional studies of the dipole polarizabilities of the linear polyacenes benzene through nonacene

Alan Hinchliffe, Beatrice Nikolaidi, Humberto Soscún Machado

Page range: 361-369

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Abstract

We report Ab Initio studies of the electric dipole polarizability of the linear polyacene series benzene through nonacene. A number of Ab Initio studies were done at different levels of theory for benzene, with all remaining Ab Initio calculations being at the B3LYP/6-311G(2d, 1p)//B3LYP/6-311+G(2d, 1p) level of theory. We find that the NN tensor component shows a constant increment of 20 atomic units per ring. AM1 and QSAR-quality empirical calculations show poor absolute agreement with the Ab Initio results but given excellent statistical correlation coefficients with the Ab Initio values. This implies that the results of such cheaper calculations can be suitably scaled for predictive purposes.

Open Access January 2, 2014

Supporting information on “2H chemical-shift resolution and dipolar 2H-1H,2H-15N correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems”

Martin Schulz-Dobrick, Ingo Schnell

Page range: SI1-SI12

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About this journal

Open Chemistry is a peer-reviewed, open access journal that publishes original research, reviews, and communications in the fields of chemistry in an ongoing way. Our central goal is to provide a hub for researchers working across all subjects to present their discoveries, and to be a forum for the discussion of the important issues in the field.

There are no submission charges. In order to sustain the production of our fully-refereed open access journal, each article accepted for publication in Open Chemistry is subject to Article Processing Charges (APC).

Special/Topical Issues:

Heterogeneous nanophotocatalysts based on polyoxometalate
Submission deadline: 31.05.2023
Phytochemicals, biological and toxicological analysis of aromatic medicinal plants
Submission deadline: 30.06.2023
Advanced Nanomaterials for Energy, Environmental and Biological Applications
Submission deadline: 31.08.2023
Marine Environmental Sciences and significance of the multidiscplinary approaches for assessing pollutions, remedies, and predictions
Submission deadline: 31.08.2023
Energy conversion and energy storage reactions
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Recent Trends in Green Chemistry
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International Symposium on Synthesis and Catalysis 2023 (IsySyCat23)
Date: 5.09 - 8.09.2023
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Submission deadline: 30.09.2023
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