Surface-Radical Mobility Test by Self-Sorted Recombination: Symmetrical Product upon Recombination (SPR).

We describe here a study of the mobility of the alkoxy radical on a surface by detection of its recombination product. A novel method called symmetrical product recombination (SRP) uses an unsymmetrical peroxide that upon sensitized homolysis recombines to a symmetrical product [R'OOR → R'O•↑ + •OR → ROOR]. This allows for self-sorting of the radical to enhance the recombination path to a symmetrical product, which has been used to deduce surface migratory aptitude. SPR also provides a new opportunity for mechanistic studies of interfacial radicals, including monitoring competition between radical recombination versus surface hydrogen abstraction. This is an approach that might work for other surface-borne radicals on natural and artificial particles.