Heterolytic bond breaking

In such breaking, one side of the molecule takes both electrons away from the electron pair. This leads to the formation of both positive and negative ions on two parts of the molecule. This can be seen, for example, during the breaking of organometallic compounds such as organomagnesium  

When ions are formed, these may have an internal energy that is higher than the energy required to induce fragmentation, thus leading to dissociation reactions such as  

This is in fact a type of homolytic ion dissociation that is classified separately because, unlike the homolytic breaking previously shown, this dissociation does not originate from molecules. 

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These reactions often are influenced profoundly by seemingly minor variations in the structure of the reactants, in the solvent, or in the temperature. It is our purpose to show how these reactions can be understood and how they can be used to prepare other useful organic compounds. But first it will be helpful to introduce the concepts of nucleophilic and electrophilic reagenfs, and to consider the AH values for heterolytic bond breaking. 

Check to see that all bonding changes are accounted for. In (a), we must draw a second arrow to show the heterolytic bond-breaking of CI2 to form Cl". 

Heterolytic bond breaking < >olart I two electrons stay with one fragment)... 

Ever since their discovery, the intimate relationship between molecular hydrogen complexes and homolytic activation of a o bond through oxidative addition has been obvious and has allowed a deeper insight into this important process. Furthermore, new visions of heterolytic activation have recently emerged [10] proton transfer from a previously coordinated a bond to another ligand seems to play a role in heterolytic bond breaking reactions much more often than expected. Thus, o complexes do not seem only to be possible intermediates in oxidative addition processes, but are also becoming compounds with a chemistry of their own (Scheme 2). 

The stability of ions depends greatly on solvation. It is inconceivable that a heterolytic bond breaking would not be highly influenced by solvent polarity. As we have just seen, a change in solvent polarity affects the rate of this reaction only very slightly. Only homolytic bond breaking is consistent with the lack of a solvent effect. 

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