Radicals ambident

As a point of reference, relative rates for methyl methacrylate have also been included in Table 6. While addition to butadiene or isoprene is significantly faster as compared to methyl methacrylate for electrophilic or ambident radicals, little rate variation is found for the 1-phenylethyl radical. 

Before we discuss the actual energetic effects of the various orbital interactions, let us take a more detailed look at the shape of the CN and CP frontier orbitals (see the contour plots in Figure 12). An important feature is their delocalized nature. In particular the SOMO, carrying the unpaired electron, has significant amplitude at both ends of the diatomic. Thus, CN and CP are clearly ambident radicals. In terms of simple valence bond structures, they are best represented as resonances 9 and 10. 

The best-known neutral ambident radicals are phenoxy radicals. Many substituted phenoxy radicals couple to give the polymers in wood, and dimerise or couple intramolecularly in the biosynthesis of a number of alkaloids, It is believed that many phenoxy radical couplings are actually the coupling of radical with radical and not of radical with neutral molecule, although the attack of a radical on a phenate ion may occasionally be an important pathway. A radical coupling with a radical is inherently a very fast process, since it is so exothermic, but only... 

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