Nitrobenzene/water systems electron transfer

Heterogeneous electron reactions at liquid liquid interfaces occur in many chemical and biological systems. The interfaces between two immiscible solutions in water-nitrobenzene and water 1,2-dichloroethane are broadly used for modeling studies of kinetics of electron transfer between redox couples present in both media. The basic scheme of such a reaction is... 

The extent to which the radicals react according to Eqs. 6 or 7 depends on the nature of Ri, Ra, and R3. If Ri = Rj = H and R3 = H through NO2, the ratio (6) (7) > 20. The addition reactions observed with these systems are characterized by strongly negative activation entropies, which can be rationalized in terms of immobilization of water molecules by the positive charge at C in the transition state [15]. That the transition state for addition has pronounced electron-transfer character concluded from the fact [15] that the rate constants for addition depend on the reduction potential of the nitrobenzene in a way describable by the Marcus relation for outer-sphere electron transfer. 

The study of electron transfer (ET) at the polarized oil (0)/water (W) (or liquid/ liquid) interface is useful for understanding not only certain catal)rtic reactions in two-phase systems (e.g., liquid membranes, microemulsions, micelles, etc.) but also energy conversion processes occurring at biomembranes. In 1979, Samec etal. [1,2] reported, as the first example, an ET between ferrocene (Fc) in nitrobenzene (NB) and Fe(CN)6 in W ... 

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