Single Electron Transfer SET in Ionic Reactions

Molecular Orbitals and Organic Chemical Reactions Student Edition Ian Fleming 2009 John Wiley Sons, Ltd 

There is good evidence that some nucleophilic substitution reactions do involve SET, but the best established use a slightly different mechanism. These are the 

Examples are the reaction of the nitronate anion 4.14 with p-nitrobcnzyl chloride 4.15, and the reaction of the pinacolone enolate 4.16 with bromo-benzene 4.17. The former might have been a straightforward SN2 reaction, but actually takes the SrnI pathway because the nitro groups make the electron transfer exceptionally easy. The latter cannot take place by a conventional Sk2 reaction, because aryl (and vinyl) halides are not susceptible to direct displacement, and the SrnI pathway overcomes this difficulty. 

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