Kinetics and Modeling of Soluble PTC

The most general model of PTC needs simultaneous consideration of all steps operative in the PTC cycle and their relative speeds and contributions to the overall rate. The actual kinetics of the reactions (with which the chemist is concerned) is part of this larger picture. Because this has been dealt with in detail by many authors (principally Starks et al., 1994), we restrict the treatment here largely to modeling with short detours into kinetics where needed. 

The PTC cycle consisting of reactions 19.1a and 19.1b is influenced by several factors. These relate to both diffusion and reaction and are briefly discussed here. 

The coefficients for the distribution of the quat species between the organic and aqueous phases are defined as 

These are often assumed to be constant during reaction, although they sometimes vary with aqueous phase ionic strength (Asai et al., 1991, 1992) and temperature (Wang and Yang, 1991a). 

Although it is usually assumed that the quat is completely ionized in the aqueous phase to form free ions and is present as an ion pair in the organic phase, in general in any solvent there can be free ions (thermodynamically distinct entities) that coexist in equilibrium with the ion pairs. Thus it is important, especially in the aqueous phase, to define a dissociation constant as 

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