Degradation of the petroleum components monomethylbenzothiophenes on exposure to light

The photochemical degradation of monomethylated benzo[b]thiophenes in aqueous solution was studied to elucidate the fate of crude oil components after an oil spill. One principal reaction pathway involves oxidation of the methyl group(s) to the carboxylic acids via aldehydes. Another pathway leads via oxidation of the thiophene ring to the quinone and then, after ring opening, to 2-sulfobenzoic acids as the ultimate products for all compounds. Opening of the benzo ring is also seen in which case thiophene aldehydes or ketones are formed.