Autooxidation reactions, basic

Another puzzling point of the mechanisms proposed to explain the autooxidation of thiols in basic solutions (in particular see Scheme 4) is the assumption that mercapto radicals dimerize almost quantitatively without interacting with the solvents in which the reaction was studied. 

The scheme depicted is not presented as an exact mechanistic representation, but rather to illustrate several basic points. First, one may observe that oxygen is a unique oxidant compared to other oxygen donors - the oxygen donors being in principle reduced relative to molecular oxygen. In fact, even the active oxidizing intermediate in metal-catalyzed autooxidation pathways is the reduced peroxo intermediate (Scheme 9.7, reaction d). In addition, only one oxygen atom of... 

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