Homolytic bond

Bond dissociation energy, D (Section 5.8) The amount of energ r needed to break a bond homolytically and produce two radical fragments. 

Table 10.1 Single-Bond Homolytic Dissociation Energies AH° at 25°C... 

N- lomoallylic enamides 239 derived from pymvate were subjected to free radical cyclization in presence of R3SnH and AIBN. The radical species generated from the C-halogen bond homolytic cleavage underwent a 5-endo-cyclization followed either by a 5-exo- or 6-fV/z/o-cyclization and reduction of the final radical species (Scheme 63)... 

Heating cleaves a weak 0-0 bond homolytically to give two oxy radicals. Fragmentation of the C1-C6 and C9-C14 bonds gives two radicals which recombine to give a cyclic diacyl peroxide. 

The bond energies listed in the table are the energies required to break the bonds homolytically to give two radicals, not heterolytically to give two ions, which is what has happened in most of the reactions we have talked about. We will look at this in much more detail in the next chapter. 

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