Coupling of Reactions at the Interface Between Immiscible Liquids

Coupling of Reactions at the Interface Between Immiscible Liquids 

we shall consider two cases of the coupHng of reactions, both of which occur at the interface. In the first case we have to deal with a reaction similar to the already-mentioned processes of of electron transfer across the oil/water interface in which 1,4-naphthaquinone, vitamin K3 and 2N-methylamino-l,4-naphthoquinone were generally used as electron acceptors. These acceptors can, however, enter into side hydroxylation reactions. Therefore, to study the coupling of reactions, we chose as an acceptor tetramethylquinone (TMQ) which is free of this shortcoming. Under these conditions it proved possible to record the coupHng of two redox reactions at the octane/water interface involving NADH, FeEP, and oxygen [56]. 

The oxygen reduction reaction is known to be accompanied by alkalization of the solution in the reaction zone. Measurement of the aqueous solution pH in the full system in air showed that in the presence of a reaction at the interface, the aqueous phase undergoes alkahzation which depends on NADH concentration and initial pH of the system (Fig. 34). When TMQ is substituted by vitamin K3 or 1,4-naphtho-quinone, no change of pH in a weakly buffered solution (5 mM tris-HCl) takes place. This can be attributed to the different structure of the reaction complex at the interface. 

Spectroscopic studies carried out in a system containing a complete set of all reaction ingredients revealed that in the course of a reaction in the inert gas atmosphere 

The TMQ reduction in the full system was also recorded chromotographically. For the purpose of control, TMQ and TMQH2 were applied to chromatographic systems. 

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