Electron transfer, partial

In such catalysis, the reaction or the catalytic site in a catalyst is always electron-deficient and, consequently, it accepts a pair of electrons from an electron donor. In the catalytic reduction of overall free energy of activation for positive catalysis, the predominant destabilization of GS or predominant stabilization of TS must involve the pair of electron transfers (partially or fully) from the reaction site in the reactant (substrate) to the reaction site in the catalyst (neutral/cationic atom/molecule). The interaction between catalyst and reactant should involve... 

Electrode processes are a class of heterogeneous chemical reaction that involves the transfer of charge across the interface between a solid and an adjacent solution phase, either in equilibrium or under partial or total kinetic control. A simple type of electrode reaction involves electron transfer between an inert metal electrode and an ion or molecule in solution. Oxidation of an electroactive species corresponds to the transfer of electrons from the solution phase to the electrode (anodic), whereas electron transfer in the opposite direction results in the reduction of the species (cathodic). Electron transfer is only possible when the electroactive material is within molecular distances of the electrode surface thus for a simple electrode reaction involving solution species of the fonn... 

Figure C3.2.7. A series of electron transfer model compounds with the donor and acceptor moieties linked by (from top to bottom) (a) a hydrogen bond bridge (b) all sigma-bond bridge (c) partially unsaturated bridge. Studies with these compounds showed that hydrogen bonds can provide efficient donor-acceptor interactions. From Piotrowiak P 1999 Photoinduced electron transfer in molecular systems recent developments Chem. Soc. Rev. 28 143-50.

The concepts of electronegativity, hardness, and polarizability are all interrelated. For the kind of qualitative applications we will make in discussing reactivity, the concept that initial interactions between reacting molecules can be dominated by either partial electron transfer by bond formation (soft reactants) or by electrostatic interaction (hard reactants) is a useftxl generalization. 

Lithium carbonate and hydrocarbon were identified in XPS spectra of graphite electrodes after the first cycle in LiPF6/EC-DMC electrolyte [104]. Electrochemical QCMB experiments in LiAsF6/EC-DEC solution [99] clearly indicated the formation of a surface film at about 1.5 V vs. (Li/Li+). However the values of mass accumulation per mole of electrons transferred (m.p.e), calculated for the surface species, were smaller than those of the expected surface compounds (mainly (CF OCC Li ). This was attributed to the low stability of the SEI and its partial dissolution. 

The partial electron transfer parameter kj is directly related to the dipole moment, Pj, of adsorbed j via ... 

Figure 6.17 shows the isotherms resulting from Eq. (6.36) for various values of the dimensionless work function n and of the partial electron transfer paramenter Xj. 

Effect of partial electron transfer parameter Figure 6.23 depicts the effect of the value of the partial charge transfer parameter A,d for fixed XA(= 0.15) on the rate enhancement ratio p(=r/r0) for the four main types of promotional behaviour, i.e., electrophobic, electrophilic, volcano and inverted volcano. The main feature of the Figure is that it confirms in general the global mle... 

In the above discussion the effect of difference in electronegativity of unlike atoms on bond length (usually a decrease) has been ignored. There is the possibility also of a small change in bond length between unlike atoms, such as of a metal and a metalloid, that reflects the difference in the nature of the overlapping orbitals, in addition to the effects of partial ionic character and of electron transfer. I believe that a thorough... 

A Mossbauer study of the protein reacted with benzaldehyde (in parallel with EPR detection of Mo(V) signals) shows partial reduction of the iron—sulfur centers, indicating the involvement of the clusters in the process of substrate oxidation and rapid intramolecular electron transfer from the molybdenum to the iron—sulfur sites. 

Benzoyl-CoA reductase carries out the two-electron reduction of the aromatic ring dnring the anaerobic degradation of benzoate by Thauera aromatica. This involves two-electron transfer from ferredoxin, and a combination of EPR and Mossbaner spectroscopy showed the presence of three different clusters, while inactivation by oxygen was associated with partial conversion of [4Fe-4S] clnsters to [3Fe-4S] clnsters (Boll et al. 2000). 

FIGURE 34.8 Free-energy surfaces for the dissociative electron transfer reaction (a) for the solvent polarization (b) along the coordinate r of the molecnlar chemical bond. corresponds to stable molecule in oxidized form. U" is the decay potential for the rednced foim. AFj and AF are the partial free energies of the transition determining mntnal arrangement of the two sets of the free-energy surfaces. 

The third term, Uqt, in Eq. (27) is due to the partial electron transfer between an ion and solvents in its immediate vicinity. The model Hamiltonian approach [33], described in Section V, has shown that Uqt (= AW in Ref. 33) per primary solvent molecule, for an ion such as the polyanion, can also be expressed as a function of E, approximately a quadratic equation ... 

Dissolving-Metal Reduction of Aromatic Compounds and Alkynes. Dissolving-metal systems constitute the most general method for partial reduction of aromatic rings. The reaction is called the Birch reduction,214 and the usual reducing medium is lithium or sodium in liquid ammonia. An alcohol is usually added to serve as a proton source. The reaction occurs by two successive electron transfer/proto-nation steps. 

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