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Ion transference

For many practically relevant material/environment combinations, thennodynamic stability is not provided, since E > E. Hence, a key consideration is how fast the corrosion reaction proceeds. As for other electrochemical reactions, a variety of factors can influence the rate detennining step. In the most straightforward case the reaction is activation energy controlled i.e. the ion transfer tlrrough the surface Helmholtz double layer involving migration and the adjustment of the hydration sphere to electron uptake or donation is rate detennining. The transition state is... [Pg.2717]

The protective quality of the passive film is detennined by the ion transfer tlirough the film as well as the stability of the film with respect to dissolution. The dissolution of passive oxide films can occur either chemically or electrochemically. The latter case takes place if an oxidized or reduced component of the passive film is more soluble in the electrolyte than the original component. An example of this is the oxidative dissolution of CrjO ... [Pg.2724]

It has been suggested that the Sommelet reaction proceeds by a hydride ion transfer, the acceptor being the conjugate acid of a Schiff base ... [Pg.693]

The mechanism of enolization involves two separate proton transfer steps rather than a one step process m which a proton jumps from carbon to oxygen It is relatively slow m neutral media The rate of enolization is catalyzed by acids as shown by the mechanism m Figure 18 1 In aqueous acid a hydronium ion transfers a proton to the carbonyl oxygen m step 1 and a water molecule acts as a Brpnsted base to remove a proton from the a car bon atom m step 2 The second step is slower than the first The first step involves proton transfer between oxygens and the second is a proton transfer from carbon to oxygen... [Pg.759]

An ionophoie may be defined as an oiganic substance that binds a polar compound and acts as an ion-transfer agent to facilitate movement of... [Pg.409]

Another big advance in the appHcation of ms in biotechnology was the development of atmospheric pressure ionization (API) techniques. There are three variants of API sources, a heated nebulizer plus a corona discharge for ionization (APCl) (51), electrospray (ESI) (52), and ion spray (53). In the APCl interface, the Ic eluent is converted into droplets by pneumatic nebulization, and then a sheath gas sweeps the droplets through a heated tube that vaporizes the solvent and analyte. The corona discharge ionizes solvent molecules, which protonate the analyte. Ions transfer into the mass spectrometer through a transfer line which is cryopumped, to keep a reasonable source pressure. [Pg.547]

The alkylate contains a mixture of isoparaffins, ranging from pentanes to decanes and higher, regardless of the olefins used. The dominant paraffin in the product is 2,2,4-trimethylpentane, also called isooctane. The reaction involves methide-ion transfer and carbenium-ion chain reaction, which is cataly2ed by strong acid. [Pg.370]

Several mechanisms have been postulated, all of which propose a hydride ion transfer as a key step. On the basis of the following results, postulate one or more mechanisms that are consistent with all the data provided. Indicate the significance of each observation with respect to the mechanism(s) you postulate. [Pg.255]

These mechanistic interpretations can also be applied to the hydrogenation of cyclohexanones. In acid, the carbonium ion (19) is formed and adsorbed on the catalyst from the least hindered side. Hydride ion transfer from the catalyst gives the axial alcohol (20). " In base, the enolate anion (21) is also adsorbed from the least hindered side. Hydride ion transfer from the catalyst followed by protonation from the solution gives the equatorial alcohol (22). [Pg.116]

Among the dynamical properties the ones most frequently studied are the lateral diffusion coefficient for water motion parallel to the interface, re-orientational motion near the interface, and the residence time of water molecules near the interface. Occasionally the single particle dynamics is further analyzed on the basis of the spectral densities of motion. Benjamin studied the dynamics of ion transfer across liquid/liquid interfaces and calculated the parameters of a kinetic model for these processes [10]. Reaction rate constants for electron transfer reactions were also derived for electron transfer reactions [11-19]. More recently, systematic studies were performed concerning water and ion transport through cylindrical pores [20-24] and water mobility in disordered polymers [25,26]. [Pg.350]

Outer sphere electron transfer (e.g., [11-19,107,160-162]), ion transfer [10,109,163,164] and proton transfer [165] are among the reactions near electrodes and the hquid/liquid interface which have been studied by computer simulation. Much of this work has been reviewed recently [64,111,125,126] and will not be repeated here. All studies involve the calculation of a free energy profile as a function of a spatial or a collective solvent coordinate. [Pg.368]

Without some additional relationship it is impossible to resolve y into and "y. By introducing an extrathermodynamic assumption as this additional relationship, it becomes possible to estimate single ion transfer activity coefficients. A widely used assumption is that the transfer activity coefficients of the cation and anion of tetraphenylarsonium tetraphenylboride, Ph4As BPh4, are equal, i.e.,... [Pg.420]

By combining these ions with other counterions, single ion transfer activity coefficients are calculated. By these techniques transfer free energies or activity coefficients have been determined for many ions and nonelectrolytes in a wide variety of solvents.Parker has discussed the extrathermodynamic assumptions that lead to single ion quantities. [Pg.420]

Table 8-8 gives some nonelectrolyte transfer free energies, and Table 8-9 lists single ion transfer activity coefficients. Note especially the remarkable values for anions in dipolar aprotic solvents, indicating extensive desolvation in these solvents relative to methanol. This is consistent with the enhanced nucleophilic reactivity of anions in dipolar aprotic solvents. Parker and Blandamer have considered transfer activity coefficients for binary aqueous mixtures. [Pg.421]

Despite this, they are good solvents for chloride-ion transfer reactions, and solvo-acid-solvo-base reactions (p. 827) can be followed conductimetri-cally, voltametrically or by use of coloured indicators. As expected from their constitution, the trihalides of As and Sb are only feeble electron-pair donors (p. 198) but they have marked acceptor properties, particularly towards halide ions (p. 564) and amines. [Pg.561]

SeOCl2 (Table 16.7) is a useful solvent it has a high dielectric constant (46.2 at 20°), a high dipole moment (2.62 D in benzene) and an appreciable electrical conductivity (2 x 10 ohm cm at 25°). This last has been ascribed to self-ionic dissociation resulting from chloride-ion transfer 2SeOCl2 SeOCl " -)-SeOCl3-. [Pg.777]

The whole sequence of reactions represents a tour de force in the elegant manipulation of extremely reactive compounds. F3CIO2 is a violent oxidizing reagent but forms stable adducts by fluoride ion transfer to Lewis acids such as BF3, AsF5 and PtFe. The structures of F3CIO2 and [F2C102] have C2v symmetry as expected (Fig. 17.26e and i). [Pg.879]

Fluoride ion transfer reactions have not been established for FBr03 and may be unlikely, (see p. 879). [Pg.881]

It will be seen that most of the dissociation constants in Table 9 lie between 10-3 and 10-11. It is of interest to know how much work is required to dissociate any of these molecules or molecular ions, transferring a proton to a distant water molecule. Using (91) in the form... [Pg.124]

Laali and Lattimer (1989 see also Laali, 1990) observed arenediazonium ion/crown ether complexes in the gas phase by field desorption (FD) and by fast atom bombardment (FAB) mass spectrometry. The FAB-MS spectrum of benzenediazonium ion/18-crown-6 shows a 1 1 complex. In the FD spectrum, apart from the 1 1 complex, a one-cation/two-crown complex is also detected. Dicyclo-hexano-24-crown-6 appears to complex readily in the gas phase, whereas in solution this crown ether is rather poor for complexation (see earlier in this section) the presence of one or three methyl groups in the 2- or 2,4,6-positions respectively has little effect on the gas-phase complexation. With 4-nitrobenzenediazonium ion, 18-crown-6 even forms a 1 3 complex. The authors assume charge-transfer complexes such as 11.13 for all these species. There is also evidence for hydride ion transfer from the crown host within the 1 1 complex, and for either the arenediazonium ion or the aryl cation formed from it under the reaction conditions in the gas phase in tandem mass spectrometry (Laali, 1990). [Pg.301]


See other pages where Ion transference is mentioned: [Pg.1941]    [Pg.2931]    [Pg.43]    [Pg.578]    [Pg.173]    [Pg.175]    [Pg.176]    [Pg.13]    [Pg.178]    [Pg.126]    [Pg.351]    [Pg.368]    [Pg.421]    [Pg.500]    [Pg.730]    [Pg.738]    [Pg.834]    [Pg.835]    [Pg.841]    [Pg.881]    [Pg.1016]    [Pg.316]    [Pg.21]    [Pg.73]    [Pg.237]    [Pg.625]    [Pg.193]    [Pg.41]   
See also in sourсe #XX -- [ Pg.85 ]




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Back electron transfer organic radical ions

Carbenium ions electron-transfer equilibria

Carbenium ions transfer

Catalysis of Acyl Transfer Processes by Crown-Ether Supported Alkaline-Earth Metal Ions

Charge transfer by ions

Charge transfer from singly charged ions

Charge transfer in neutral atom-multiply charged ion collisions

Charge transfer multiply charged ions

Charge transfer, and ion—molecule reactions

Charge-Transfer Coordination to Metallocomplex Ion-Radicals

Charge-transfer complexes and radical ion salts

Chloride ion transfer

Chloride-ion transfer reactions

Contact ion pairs electron-transfer oxidation

Coupled electron-ion transfer

Crystals of Molecules with Charge Transfer, Radical-ion Salts

ELECTRODE REACTIONS IN ION TRANSFER

Electrochemical ion transfer reactions

Electrode potential in ion transfer equilibrium

Electron Transfer System Coupled to Oxidation of Ferrous Ion

Electron Transfer to and from Diazo Compounds Ion Radicals

Electron transfer like charge radical ions

Electron transfer metal ions

Electron transfer mixed valence ions

Electron transfer organic radical ions

Electron transfer oxidized ions

Electron transfer reduced ions

Electron transfer, between metal ions

Electron transfer, between metal ions Marcus theory

Electron transfer, between metal ions inner sphere

Electron transfer, between metal ions outer sphere

Electron-Transfer Equilibria for Contact Ion Pairs

Electron-Transfer Reactions Involving Transition-Metal Ions

Electron-Transfer Reactions with Participation of Ion-Radical Aggregates

Electron-transfer in outer-sphere reactions of metal ions

Electron-transfer oxidation radical ions

Electrostatic Free Energy of Ion Transfer

Energy Transfer Between Two Rare Earth Ions

Energy transfer between ions

Energy transfer between organic ligands and rare earth ions

Energy transfer from transition metal ions

Energy transfer from transition metal ions elements

Equilibrium potential of ion transfer reactions

Excited ions charge transfer

Excited ions heavy particle transfer

Facilitated ion transfer

Fluoride-ion transfer reactions

Free energy of ion transfer

Gibbs energy change on transfer of ions from water to organic

Gibbs energy of ion transfer

Group transfer potential effect of metal ions

Halonium ion transfer

Heavy ion induced transfer

Heavy ion induced transfer reactions

Hydride Ion Shift and Transfer Reactions

Hydride Ion, Proton and Carbocation Transfer to Monomer

Hydride ion transfer

Hydride transfer to cyclic oxonium ion

Hydrogen ion transfer

Hydrogen, Hydride Ion, and Electron Transfer

Interface between two immiscible electrolyte solutions ion transfer

Interfacial ion transfer

Ion Transfer Energies and Galvani Potentials

Ion Transfer into Solvent Mixtures

Ion Transfer through a Protective Film

Ion Transfer through an Adsorbed Phospholipid Monolayer

Ion Transference Number

Ion and proton-transfer

Ion pair charge transfer

Ion transfer

Ion transfer

Ion transfer at the ITIES

Ion transfer coupled

Ion transfer energy

Ion transfer models

Ion transfer resistance

Ion transfer voltammetry

Ion transfer, and electron

Ion-Assisted Phosphoryl Transfer Reactions

Ion-transfer mechanism

Ion-transfer optics

Ion-transfer polarography

Ion-transfer potential

Ion-transfer reactions

Ions Transfer of Electrons

Kinetics of ion transfer

Lanthanide ions charge transfer

Limitations ions transfer

Magnesium ions group transfer

Marcus Theory for Ion-Transfer Reactions

Mass-Transfer Rates in Ion Exchangers

Mass-transfer mechanisms and kinetics ion-exchange membranes

Mechanism for transfer of Br+ from bromonium ion

Metal ion coupled electron-transfer

Metal ion transfer in a series of two elementary steps

Metal ion transfer in a single elementary step

Metal ion-coupled electron transfer MCET)

Metal ions group transfer

Metal-ion transfer

Microdroplets, mass transfer and reaction rates ion-pair extraction of anionic surfactant with

Mixed ion-transfer potentials

Models of Bond-Breaking Ion and Electron Transfer Reactions

Negative ion transfers

Negative ions charge transfer

Negative ions proton transfer

Nernst Equation for Ion Transfer

Nitrogen ions change transfer mechanism

Nucleophilic and Electron-Transfer Processes in Ion-Pair Annihilation

Oxide ion transfer

Oxygen ion transfer

Passivity ion transfer

Photochemically Induced Ion Transfer

Photoinduced electron transfer transition metal ions

Photoinduced electron transfer, catalysis metal ions

Positive ions charge transfer

Positive ions hydride transfer

Positive ions proton transfer

Potassium ion transfer

Proton- and ion-transfer reactions

Redox ions, electron transfer

Redox ions, electron transfer reactions

Si Slicing and Layer Transfer Ion-Cut

Sodium ion transfer

Standard Gibbs energy of ion transfer

The Mechanism of Ion Transfer

Transfer chemical potentials metal ions

Transfer number, oxygen ions

Transfer of hydride ion

Transfer of ions

Transference number complex ions from

Transference number of an ion

Transference numbers, of ions

Transference of lithium ions

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