Kinetics of Radical Ion Fragmentations

The stereoelectronic effects discussed in Sect. 3.3 are also illustrated by the data in Table 1. Thus, the meta derivatives fragment slower than para isomers an increase in the spatial separation between the n system and the scissile bond lowers the rate of fragmentation and substituents increasing the extent of charge delocalization in the transition state accelerate the cleavage [99, 106]. 

The limited available data suggest that solvent has relatively small effect on the fragmentation rate, although the change in solvent may affect the relative magnitudes of entropy and enthalpy of activation [102], For those reasons the 

A free-energy relationship for mesolytic cleavage of C-C bonds in 7t-radical ions of bicumene derivatives [78, 99, 102]. The solid line represents a hypothetical reaction with no overhead (km = (kbJ /h)exp( — AG J(R T)), i.e. one with only the thermodynamic barrier). The broken lines are the best-fit lines to parabolic (Marcus-type) and hyperbolic (Weller-type) functions. 

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