X4. Zwischenreaktionen bei photosensibilisierten Prozessen in Lösungen

The O2‐transfer to organic acceptors (A) like α‐terpinene is photosensitized by dyestuffs (Sens). This transfer, which has a quantum yield ≤ 1, leads to peroxides (AO2) like ascaridol and takes place as cyclic catalysis according to scheme 1. We studied the quantum yields as a function of T, η/T and with different A's in the range of + 20 to ‐ 160°C and with viscosities (η) of 0.05‐5 poises. The heats of activation, EA, of the reactions equation image were determined, the diffusion processes occuring previously being taken into consideration (Tab. 4). In ascaridol synthesis the EA of all subprocesses (except diffusion) of the sensitizer cycle lie below 1 kcal/mol. Similar results were obtained with A = furane, 2,5‐dimethylfurane, cyclohexadiene‐(1,3) and triphenylphosphine. The duration of the sensitizer cycle of ascaridol synthesis with Bengal rose (BR) in methanol was found to be between 2 · 10−7 and 4 · 10−7 sec. Experiments with the greatest radiation intensity of our apparatus showed in another manner that the cycles definitely have a duration less than 10−6 sec.