Radical-Site Initiation a-Cleavage

Equations 4.9 to 4.12 summarize the homolytic dissociations (McMurry 1984) discussed in this section. 

Reaction initiation at the radical site arises from its strong tendency for electron pairing the odd electron is donated to form a new bond to an adjacent atom. This is accompanied by cleavage of another bond to that a-atom thus this is commonly called the a-cleavage reaction  

The driving force is like that underlying the high reactivity of neutral radicals in processes such as dimerization and hydrogen abstraction. The tendency for the radical site to initiate a reaction in competition with the charge site generally parallels the radical site s tendency to donate electrons N S, O, rc, R - Cl, Br H, where n signifies an unsaturated site and R- an alkyl radical. (This 

Ionization of an aliphatic ether (Equation 4.13) should occur preferentially by loss of an n-electron of the oxygen. Donation of the unpaired electron to the adjacent C—O bond is followed by transfer of an electron from another bond of this a-carbon atom. The resulting one-electron bond then cleaves to give the alkyl radical and the resonance-stabilized oxonium ion the greater the doublebond character of this ion, the lower will be the critical (activation) energy of the reaction. Note that only the radical site moves the charge site remains on the oxygen. 

Unknown 4.2. Predict which will be the most-abundant product ion in the mass spectrum of HO—CH2—CHj—NH2. 

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For the radical site initiation (a cleavage), the tendency for electron pairing drives the formation of a new bond to an adjacent atom to the radical site and the cleavage of a bond to an a atom. 

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