Starks catalytic cycle

In order to confirm that the precatalyst initiation rate is slower than the catalytic cycle, we devised a simple experiment in which the kinetic profile of the reaction is monitored upon addition of fresh reactants at the end of the reaction (Figure 5.7) [16]. Usually, this protocol is used to probe catalyst longevity and gives rise to slower reaction upon successive additions. In stark contrast, an eightfold increase in rate, relative to the initial reaction rate (curve A), was observed upon the second addition of fresh reactants (curve B). Even more... 

Once the nucleophile or base (represented by Nu) is in solution in nonpolar (organic) media, the displacement or deprotonation can take place with product formation. In the case of a nucleophilic displacement reaction, would ultimately be ion-paired with the nucleofuge. If the leaving group were X, the ion pair QX would be generated and would be subject to the equlibria formulated above. Starks has offered a now classic diagram of the phase transfer catalytic cycle [10a]. 

Starks phase transfer catalytic cycle diagram... 

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