Fragmentation charge center initiation

The secondary process of amine fragmentation (1,3-sigmatropic shift) may be used as an example of a process initiated by the charge center (Scheme 5.18). 

The charged and radical centers may coincide (e.g., elimination of n-electron) or may be separated (e.g., ionization of rr-bond). These centers may be quite far away from one another in the fragment ions. For example, SO2 loss from the molecular ion of tetrahydrothiophendioxide initially leads to a linear chain of four methylene groups, while the charge and the unpaired electron are located at the opposite ends of the chain. Certainly such an ion may further isomerize into a more stable structure. 

Unknown 2. Propose the reactions initiated by the charge and radical centers, which will take place during fragmentation of the M+ of the following compounds ... 

Ten years later Napper and Alexander, in studying the kinetics of vinyl acetate polymerization in the presence of anionic, cationic and nonionic emulsifiers arrived at the same conclusions as Priest s, although they did not cite his work (13). They also observed an acceleratory effect of added emulsifier like that found by Baxendale et al. (8), but they seemed unaware of that work as well. They showed that when the charge on primary particles (due to initiator fragments) was opposite to that of the emulsifier, the rate of polymerization was slower than that in the absence of emulsifier. This was presumably due to the greater instability of the colloid formed and the consequent production of fewer polymerizing centers. 

For practical applications in polymer dispersions (ie also during heterophase polymerizations) the effect of charge stabilization due to permanent charges, either by ionic stabilizers, comonomers, or initiator fragments, is much more important. The repulsive potential between two equally charged particles (yR,es) separated at a center-to-center distance of (dpp + D) is given by equation 35, where Q is the charge on each particle and a is the permittivity of the continuous phase. 

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