Electron-transfer mechanism another possible

In principle, if the X values for a set of like reactions are similar to one another, and W r) is small or constant, a plot of AG versus AG° will be linear and have a slope of 0.5. As noted above, it is rarely possible to measure AG values directly. An alternative option for plotting data using a linear relationships is to use Equation 1.15 and the definition of the equilibrium constant, K = A exp( AG° // 7), in which A is a constant. If the equilibrium constants for a series of reactions can be measured or calculated, one can plot In A versus In AT (Equation 1.15). A linear result with a slope of 0.5 is indicative of a common outer-sphere electron transfer mechanism. 

NEts used in order to neutralize HX also probably plays the role of a reducing agent of Pd to Pd°. The reduction potential being low, the single-electron-transfer mechanism to Pd is a viable pathway. Another possible reduction route is (3-elimination subsequent to coordination ... 

There is another possible mechanism for addition of organometallic reagents to carbonyl compounds. This involves a discrete electron-transfer step. °... 

The latter reaction must involve a large number of molecular steps and may be a much slower process. The mechanisms of a few inorganic electron transfer processes have been summarized by Taube (1968). The presence of very slow reactions when several redox couples are possible means that the Eh value measured with an instrument may not be related in a simple way to the concentrations of species present, and different redox couples may not be in equilibrium with one another. Lindberg and Runnells (1984) have presented data on the extent of disequilibrium... 

Another possible mechanism also involves a methyl radical (mechanism 3). In this case, electron transfer from one of the reduced clusters on CODH/ACS to methyl-Co(III) would form a methyl-Co(II) species that can disproportionate to form Co(I) and methyl-Ni(II). 

Another interesting situation which demonstrates the role of solvation on cluster reactions, with particular relevance to identifying mechanisms of possible importance in the condensed phase, concerns the initiation of electron transfer reactions. Interesting examples include those initiated through Penning ionization.161... 

Thus, two routes of transformation are possible for the Fe2+(H202) complex one-electron transfer to form the hydroxyl radical and two-electron transfer to form the ferryl ion. It is difficult to prove experimentally the formation of the ferryl ions because they are very reactive, so that this route of interaction of H202 with Fe2+ remains hypothetical to a great extent. Another change in the mechanism of H202 decomposition with increasing pH is related to the acidic dissociation of H02 (pKa = 4.4)... 

It should be noted that the conditions that make possible the occurrence of an ECE mechanism, involving the reduction of C at the electrode surface, involve the possibility of another mechanism in which the second electron is transferred from B to C rather than from the electrode as pictured in Scheme 2.5. This homogeneous electron transfer reaction may be viewed as a disproportionation reaction insofar that A has one oxidation number more than B and C, and D, one oxidation number less. 

The possibility that there might be long-range electron transfer between redox-active centers in enzymes was first suspected by biochemists working on the mechanism of action of metalloenzymes such as xanthine oxidase which contain more than one metal-based redox center. In these enzymes electron transfer frequently proceeds rapidly but early spectroscopic measurements, notably those by electron paramagnetic resonance, failed to provide any indication that these centers were close to one another. 

In an another mechanistic study, Foote and co-workers reported a possible charge-transfer mechanism for the photochemical [2+2] cycloadditions of electron-rich ynamines [56-58]. Further studies on the regio- and stereoselectivity upon addition of less electron-rich substrates such as alkyl-substituted 1,3-bu-tadienes [59], acyclic enones [60], and aryl alkenes [61] to C60 were performed in more recent years. 

Banks and coworkers refer to possible S 2 or ET mechanisms. They emphasized that a feature common to both mechanisms is the generation of nitranion (36) and hence the release of the highly electrophilic perfluoro-l-azacyclohex-l-ene (35). Their schemes are illustrated in equation 61. However, we believe another mode of electron transfer should... 

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