Results have revealed that rose oxide forms about in same ratio as by employment of rose bengal sensitizer. Product analysis has shown that rose oxide forms in similar yield. Chen et al. It is known that perylene diimide forms only super oxide anion radical, through a singlet state electron transfer, and super oxide anion radical forms hydrogen peroxide by a hydrogen abstraction from the olefin. As seen on the scheme below, photosensitized oxygenation proceeds by an electron transfer from exciplex to oxygen, that results in formation of superoxide anion radical.
Final product is rose oxide, by the hydrogen abstraction of hydroperoxyl intermediate.
Perylene diimide do not degrade at all under high intensity of solar light and may be re-used by alcohol addition precipitation. It is expected that super oxide anion radical reaction with citronellol gives similar hydroperoxy intermediates as formed at singlet oxygen reaction. GC-MS spectrums show that rose oxide is produced at final step. G. Ohloff, E. Klein and G. O. Schenk, Angew.