Atmospheric photooxidation of alkylbenzenes—II. Evidence of formation of epoxide intermediates

Photooxidation experiments of six alkylbenzene compounds were conducted under simulated atmospheric conditions. Carbonyl products with their molecular weights matching a series of epoxide carbonyls were observed. This observation supports the supposition formation of epoxide intermediates as suggested by Bartolotti and Edneyʹs theoretical calculations. These epoxide intermediates are also consistent with recently observed prompt HO2 formation upon hydroxyl radical attack on the ring. An alternative origin of the observed epoxides might be from a second OH attack upon the epoxide/oxepin intermediate proposed by Barnes et al. (1996, Air & Waste Management Association 89th Annual Meeting and Exhibition, Nashville). Because of the potential toxicity and mutagenicity of the epoxide products, the atmospheric chemistry of these epoxide compounds should be studied in greater detail with indoor and outdoor chamber and in field experiments to assess their role in the urban atmosphere.