Quaternary transport rate constants

Q cycle a series of reactions in the electron transport chain that provides the link between two-electron transfers and one-electron transfers (20.3) quaternary structure the interaction of several polypeptide chains in a multisubunit protein (4.1) rate constant a proportionality constant in the equation that describes the rate of a reaction (6.3) rate-limiting step the slowest step in a reaction mechanism it determines the maximum velocity of the reaction (6.3)... 

Figure 15 Determination of the rate constants kj and kj of the transport of homologous quaternary alkylammonium bromides in a three-compartment model system. Water/n-octanol/water system (upper diagram) and time dependence of substance concentrations in the different compartments after different times t (lower diagram) (reproduced from Figures 1 and 4 of ref. [443] with permission from Editio Cantor Verlag GmbH, Aulendorf, Germany).

In these reactions the quaternary salt transports the carbanion from the interface into the organic phase where the reaction occurs. This was proved as follows i) the deeply coloured 9-fluorenyl anion was transported into the organic phase from the interface by equilibrating an aqueous 50% NaOH solution with a solution of fluorene in benzene in the presence of Hex4N Cl ii) stirring rates must be at least 750-800 rpm to obtain reproducible results in the generation of dihalocarbenes starting from chloroform and 50% NaOH in the presence of a quaternary salt this is consistent with the typical behaviour of interfacial reactions, since usual PTC reactions proceed at a constant rate over 250-300 rpm (see Sect. 2.3.1). 

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