When studying the mechanism (Fig ) of the photooxygenation of α-terpinene to ascardidole we identified multiple steps in the process that might be susceptible for improvement by more efficient mixing; e.g., the formation of singlet oxygen via excited RB and the subsequent oxidation of α-terpinene to ascardidole due to the short life time of singlet oxygen (16 µs in ethanol). The overall reaction scheme for the photooxgenation of α-terpinene. A) photocatalytic pathway to ascaridole B) photosensitized pathway to side products C) autooxidation pathway to side product. 2 Results & Discussion (2), the reaction was much faster in a microreactor in comparison to batch. This has previously been illustrated by other researchers and is attributed to better light penetration and improvements in mass transfer and mixing. This ratio was also used in the microreactor (a higher oxygen concentration showed more selective ascaridole formation ). The findings, illustrated in Fig , were quite interesting.