Abstract: The primary processes in UV photolysis and photooxidatiou of 14 aromatic aldehydes have been studied by the combinatiou of spin trapping technique and ESR spectroscopy. The results show that:
1. The main active intermediates in photolysis of 10 substituted aromatic aldehydes are aromatic amido radicals ϕĊO.
2. Active radicals formed in the primary processes of photooxidation are the same as those formeb in the photolysis processes, and accumulation rates of free radicals in photooxidation are faster than those in photlysis. So it is sure that the formation of free radicals are accelerated owing to the hydrogen abstraction from aldehydes by oxygen.
3. No active radicals have been detected for OH substituted aromatic aldehydes.