Alkoxy radicals reactions, intermediacy

In many cases both homolytic and heterolytic pathways afford the same products, e.g. alcohols and ketones from hydrocarbons, which means that results have to be interpreted with care. Certain elementary tests for homolytic pathways need to be performed, e.g. inhibition by a radical scavenger such as lonol indicates a free radical chain mechanism and loss of yield on flushing with an inert gas suggests the intermediacy of dioxygen in reactions with H2O2 or RO2H. More sophisticated reality tests can also be performed to demonstrate the intermediacy of alkoxy radicals in oxidations with RO2H [17]. 

Two mechanisms have been considered for the self-reaction of primary and secondary alkylperoxy radicals, the Russell mechanism (lO) reactions (26), (27), and (28) and a mechanism involving the intermediacy of alkoxy radicals ( 3, kk) reactions (29), (30), (31), and (32). The reactions involved in these two mechanisms are presented in Scheme II. 

Ethoxyethylperoxyls were prepared by a variety of methods and react to give ethyl acetate, ethanol, acetaldehyde and ethyl formate. (Table V). There was no evidence for the formation of di-(1-ethoxyethyl) peroxide, a result that is not entirely incompatible with Diaper s work in view of the large difference in the size the peroxy radicals studied by the two groups of workers. The absolute yields of the products were difficult to ascertain with any degree of certainty because of secondary reactions. The high yield of ethyl formate is, however, diagnostic for the intermediacy of alkoxy radicals and indicates that at least 20 of the self-reactions of 1-ethoxyethylperoxyls occur via the radical mechanism. 

Forbes JE, Zard SZ. A novel radical chain reaction of xanthic anhydrides. Further observations on the intermediacy of alkoxy-thiocarbonyl radicals in the Barton-McCombie reaction. Tetrahedron Lett. 1989 30 4367-4370. 

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