Homolytic cleavage, definition

In this chapter, the basic principle of arrow pushing was introduced in the context of organic reactions driven by homolytic cleavage, heterolytic cleavage, or concerted mechanisms. Furthermore, the concept of polarity was introduced using heteroatoms and common organic functional groups. This discussion led to the definitions of nucleophiles and... 

The separate and quantitative evaluation of accelerating steric effects on the homolytic cleavage of C—C-bonds allowed the definition of intrinsic barriers for the bond dissociation reaction, i.e. AG or AH at Hs = 0 in Fig. 2 or 3 or in Eq. (1-11) in general. AH is equal to or slightly than the corresponding bond dissociation energy (BDE) 6a-811 as pointed out earlier. 

Energy of a homolytic cleavage of communication OH (Z) of hindered phenols is an efl cacy qirantity indicator in reactions inhibiting oxidations. Experimental results of definition D [1-3] are known. In... 

A definite proof that no homolytic cleavage of the M-M bond is involved was obtained on the Re2 carbonyls ... 

On the other hand, as shown by the left-hand side of eqn (8.18), Katrp depends upon the relative values of the C-X and Cu X dissociation energies, in other words to Kbh and Knaio (Knaio is, as seen from its definition in Figure 8.6, the inverse of the Cu -X bond dissociation energy). The lower than expected difference between Katrp(RCI) and KATRp(RBr), based solely on the ease of homolytic cleavage (Kbh) of C-X bonds, can be explained also by the greater stability of the Cu -Cl compared to Cu -Br bond, i.e., higher chloro-than bromophilicity of Cu complexes. ... 

Photogeneration of MnRe(CO)io from irradiation of both Mn2(CO)io and Re2(CO)io also occurs, and such cross-coupling has become a definitive test of whether homolytic metal-metal bond cleavage occurs. Kinetics of recovery of ground state Mn2(CO)io absorption after flash irradiations are consistent with formation of Mn(CO)5 radicals from the excitation (13). 

---