Application to organic redox systems

In the same work, encumbered stilbenes were found to have much higher intrinsic barriers than the hydrocarbons listed in the caption of Fig. 3. This is due to a strong internal reorganization around the central C—C bond (Dietz and Peover, 1968). Similar effects have been found in the reduction of cyclooctatetraene and related systems (see Evans and O Connell, 1986, and references cited therein). 

Another important aspect of the Marcus theory has also been systematically investigated with organic molecules, namely the quadratic, or at least the non-linear, character of the activation-driving force relationship for outer sphere electron transfer. In other words, does the transfer coefficient (symmetry factor) vary with the driving force, i.e. with the electrode 

These findings contrast with the results of one investigation of the electrochemical kinetics of the iii/ii couple series of chromium complexes (Weaver and Anson, 1976) where the transfer coefficient was found not to 

Another example where a does not appear to vary with potential is the hydrogen evolution reaction (39) in water (Conway, 1985). It should. 

Another, and even more striking aspect of the variation of the symmetry factor with the driving force is the prediction, from (9) and (10), that an inverted region should exist at large driving forces, i.e. when the inequality (40) applies. The activation free energy is then predicted to increase with the 

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Modelling of outer sphere electron transfer 5 Application to organic redox systems 15 Modelling of dissociative electron transfer 21 Stepwise and concerted processes 23 Aryl halides 37 Alkyl halides 54 Other examples 63... 

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