Ferf-Butoxy oxygen

Nucleophilic and electrophilic radicals abstract different hydrogen atoms from butyrolactone 7.10 the ferf-butoxy radical selectively abstracts a hydrogen atom from the methylene group adjacent to the oxygen atom, whereas a boryl radical abstracts a hydrogen atom from the methylene group a to the carbonyl group. 

A common feature of all radical initiators is a relatively weak bond that readily undergoes homolytic cleavage. In all but one of the radical initiators shown in Table 28.3, the weak bond is an oxygen-oxygen bond. Two factors enter into the choice of radical initiator for a particular chain-growth polymerization. The first is the desired solubility of the initiator. For example, potassium persulfate is often used if the initiator needs to be soluble in water, whereas an initiator with several carbons is chosen if the initiator must be soluble in a nonpolar solvent. The second factor is the temperature at which the polymerization reaction is to be carried out. For example, a ferf-butoxy radical is relatively stable, so an initiator that forms a fert-butoxy radical is used for polymerizations carried out at relatively high temperatures. 

The reaction of a tryptophan derivative, N- tert-butoxycarbonyl)-L-tryptophan, with hypoxanthine/ xanthine oxidase/Fe(III)-EDTA mainly resulted in the oxygenation of the pyrrole ring of the indole nucleus (Itakura etal. 1994). 2-[(ferf-Butoxy-carbonyl)-amino]-3-(3-indolyl)propionic acid and N- (fer f-butoxycarb onyl) -hT-formylkynurenine were identified as the major products. 

This mechanism, involving a free radical R , is compatible with the allylic rearrangements found The finding that ferf-butyl peroxyesters labeled with in the carbonyl oxygen gave ester with 50% of the label in each oxygen is in accord with a combination of R. with the intermediate 32, in which the copper is ionically bound, so that the oxygens are essentially equivalent. Other evidence is that tert-butoxy radicals have been trapped with dienes.Much less is known about the mechanisms of the reactions with metal acetates. 

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