Free radicals, definition oxidation types

At this type of meeting one becomes keenly aware of the controversial and unsolved problems that exist in the field under discussion. To put these problems in better perspective, I should like to spend some time discussing three points (1) areas of agreement which have been reached in the field of free radical oxidation (2) problems which are definitely unsettled at the moment, and about which there appears to be appreciable controversy (3) and finally, some of the unknown features of oxidations whose parameters are still not resolved. 

What do we mean by oxygen activation A reasonable working definition is catalysis of the oxidation of a hydrocarbon substrate by 2 not involving a classical free radical autoxidation mechanism or direct oxidation by a metal salt. The latter stipulation is needed to exclude Wacker-type oxidation processes in which the oxygen in the product is, initially at least, derived from water. On the other hand, it should not matter whether dioxygen complex formation precedes or follows the oxidation of the substrate by an oxometal complex (see Figure 4). The former pertains to liquid and the latter to gas phase processes. 

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