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Ion Transfer (ion + transfer)

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Chemistry100%

Selected Abstracts

Advances in the Study of Ion Transfer at Liquid Membranes with Two Polarized Interfaces by Square Wave Voltammetry

ELECTROANALYSIS, Issue 14 2010
A. Molina
Abstract A general analytical expression has been deduced for the I/E response of the square wave voltammetry corresponding to ion transfer processes in systems with two liquid/liquid polarized interfaces. This expression has been evaluated through the experimental study of a series of quaternary ammonium cations and metal chloro complex anions. We have found that systems with two liquid/liquid polarizable interfaces present the striking advantage that the difference between peak potentials of square wave voltammograms of cations and anions with similar standard ion transfer potential is much greater than in systems with a single polarizable one. [source]

Electrochemical Investigation of Heavy Metal Ion Transfer Across the Water/1,2-Dichloroethane Interface Assisted by 9-Ethyl-3-Carbazolecarboxaldehyde-Thiosemicarbazone

ELECTROANALYSIS, Issue 12 2007
Haluk Bingol
Abstract The transfer of heavy metal ions across the polarized water/1,2-dichloroethane (1,2-DCE) interface assisted by 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) in the 1,2-DCE phase has been studied by cyclic voltammetry. Voltammetric waves of Pb(II) and Cd(II) ions were reversible and quasi-reversible, respectively, whereas that of Hg(II) and Zn(II) ion were irreversible. The voltammogram of Cu(II) ion showed a two-step wave, however the nature of the transfer could not be satisfactorily evaluated by analyzing the cyclic voltammetric data. When Ni(II) and Co(II) was used no peak was visible under the experimental conditions used in this study. The dependence of the half-wave potentials of Pb(II) and Cd(II) ions on the ligand concentration reveals that their ion-transfer is assisted by the formation of 1:3 metal-ECCAT complex in 1,2-DCE. The over-all association constants of [Pb(ECCAT)3]2+ and [Cd(ECCAT)3]2+ complexes in DCE-phase have been determined to be log ,=14.03 and log ,=15.44, respectively. [source]

Voltammetric Elucidation of Ion Transfer Through an Extremely Thin Membrane

ELECTROANALYSIS, Issue 9 2004
Nobuyuki Ichieda
Abstract Digital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1,mm to 10,nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10,nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10,nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10,13 to 10,14,cm2 s,1). [source]

Rearrangement with Oxide Ion Transfer in Reactions of 4-Chloro-2-oxo-2,3-dihydrothiazole-5-carbaldehyde with Ureas.

CHEMINFORM, Issue 51 2006
4-Dioxothiazolidin-5-ylidenemethyl)ureas., cis-(Z), trans-(E) Isomerism of N-(
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Sulfide Ion Transfer from a Vicinal Dithiolate.

CHEMINFORM, Issue 9 2006
A New Route for the Synthesis of Mesocyclic Trithiaethers.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Voltammetric Elucidation of Ion Transfer Through an Extremely Thin Membrane

ELECTROANALYSIS, Issue 9 2004
Nobuyuki Ichieda
Abstract Digital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1,mm to 10,nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10,nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10,nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10,13 to 10,14,cm2 s,1). [source]

Membrane embedded location of Na+ or H+ binding sites on the rotor ring of F1F0 ATP synthases

FEBS JOURNAL, Issue 22 2002
Christoph Von Ballmoos
Recent crosslinking studies indicated the localization of the coupling ion binding site in the Na+ -translocating F1F0 ATP synthase of Ilyobacter tartaricus within the hydrophobic part of the bilayer. Similarly, a membrane embedded H+ -binding site is accepted for the H+ -translocating F1F0 ATP synthase of Escherichia coli. For a more definite analysis, we performed parallax analysis of fluorescence quenching with ATP synthases from both I. tartaricus and E. coli. Both ATP synthases were specifically labelled at their c subunit sites with N -cyclohexyl- N, -(1-pyrenyl)carbodiimide, a fluorescent analogue of dicyclohexylcarbodiimide and the enzymes were reconstituted into proteoliposomes. Using either soluble quenchers or spinlabelled phospholipids, we observed a deeply membrane embedded binding site, which was quantitatively determined for I. tartaricus and E. coli to be 1.3 ± 2.4 Å and 1.8 ± 2.8 Å from the bilayer center apart, respectively. These data show a conserved topology among enzymes of different species. We further demonstrated the direct accessibility for Na+ ions to the binding sites in the reconstituted I. tartaricus c11 oligomer in the absence of any other subunits, pointing to intrinsic rotor channels. The common membrane embedded location of the binding site of ATP synthases suggest a common mechanism for ion transfer across the membrane. [source]

Kinetics and mechanism of the oxidation of some ,-hydroxy acids by 2,2,-bipyridinium chlorochromate

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2002
Vinita Kumbhat
The oxidation of glycolic, lactic, malic, and a few substituted mandelic acids by 2,2,-bipyridinium chlorochromate (BPCC) in dimethylsulphoxide leads to the formation of corresponding oxoacids. The reaction is first order each in BPCC and the hydroxy acids. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b [H+]. The oxidation of ,-deuteriomandelic acid exhibited a substantial primary kinetic isotope effect (kH/kd = 5.29 at 303 K). Oxidation of p -methylmandelic acid was studied in 19 different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 248,254, 2002 [source]

Charge and Mass Transfer Across the Metal/Solution Interface

ISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008
Eliezer Gileadi
Electrode reactions are characterized by charge transfer across the interface. The charge can be carried by electrons or by ions. It is shown here that when both mass and charge cross the interface, the charge must be carried by the ionic species, not by the electrons, as a result of the very large difference in the time scale for electron and ion transfer. A prime example of charge transfer by ions is metal deposition. It is proposed that ion transfer occurs by migration of the ions across the interface, under the influence of the high electrostatic field in the double layer. The rate constants observed for metal deposition are comparable to those for outer-sphere charge transfer. These unexpectedly high rate constants for metal deposition are explained by a model in which removal of the solvation shell and reduction of the effective charge on the metal ion occur in many small steps, and a make-before-break mechanism exists, which lowers the total Gibbs energy of the system as it moves along the reaction coordinate from the initial to the final state. [source]