Homogeneous electron exchange reactions

This chapter attempts to survey the studies which have been made on the various electron transfer reactions, occurring between metal ions (of the same element) in homogeneous solution. These reactions include the types known as exchange reactions... 

Esr spectroscopy has also been used to study pure solvent dynamics in electron self-exchange reactions (Grampp et al., 1990a Grampp and Jaenicke, 1984a,b). When the systems are not linked by a spacer (i.e. TCNQ- /TCNQ (TCNQ = tetracyanoquinodimethane), the homogeneous bimolecular rate constants /chom are given by (10), with fcA the association constant and kET... 

Here, i is the faradaic current, n is the number of electrons transferred per molecule, F is the Faraday constant, A is the electrode surface area, k is the rate constant, and Cr is the bulk concentration of the reactant in units of mol cm-3. In general, the rate constant depends on the applied potential, and an important parameter is ke, the standard rate constant (more typically designated as k°), which is the forward rate constant when the applied potential equals the formal potential. Since there is zero driving force at the formal potential, the standard rate constant is analogous to the self-exchange rate constant of a homogeneous electron-transfer reaction. 

In alkaline 252 is formed in the first reduction and can be isolated when working at low temperature. Further reaction involves loss of water and fast homogeneous electron exchange between 253 and 252 with formation of 251 and product 254 [Eq. (135)]. 

In homogeneous electron exchange reactions between two species differing only in their valence states, AF is given by Equation 10 with X equal to 2X2 and (AF0,int — w) replaced by AFot — uf + wp (5). (uf... 

The simplest elementary act in homogeneous solution chemistry is the exchange of an electron between two chemical entities. No bonds need to be formed or broken in the process, and if the two species are identical, except for a difference in oxidation state, no net chemical change takes place (1). Such self-exchange reactions, although of no chemical consequence, constitute the basis of theoretical treatments of electron transfer. 

Homogeneous charge transfer can take place between chemically similar redox species of one redox couple, e.g., Fe3+ and Fe2+ ions in solution or ferrice-nium and ferrocene moieties in poly(vinylferrocene) films, the electron transfer (- electron hopping or electron exchange reaction) can be described in terms of second-order kinetics and according to the - Dahms-Ruff theory [viii-x] it may be coupled to the isothermal diffusion ... 

Ew, any characteristic potential of the wave E1/2, Ep, Ep/2, E°, standard reduction potential of the electron transfer step, involving an exchange of n electrons (n > 0 for a reduction n < 0 for an oxidation). intrinsic standard heterogeneous rate constant k, rate constant of the homogeneous follow-up chemical reaction. Chemically reversible or irreversible (see footnote page 55). 

Marcus has developed his primarily classical theory for electron transfer reactions in homogeneous solutions. In the simplest type of reaction a single electron is transferred without breaking or forming bonds. A bimolecular exchange reaction is given by... 

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