The photolysis of hexaaquoiron(III) perchlorate in the presence of ethylene glycol

Two types of reactions occur when hexaaquoiron(III) ion is irradiated at 254 nm in the presence of alcohols. Firstly, a charge transfer transition from a water centred orbital to an iron centred orbital produces OH•radicals which go on to abstract hydrogen from the alcohols. Secondly, |the reaction with the charge transfer excited states of iron(III) species can lead to outer sphere oxidation of the alcohols. In this paper, these reactions have been studied in detail for the diol ethylene glycol in aqueous solutions. It has been found that the quantum yield of acetaldehyde, the major product of hydroxyl radical reactions with ethylene glycol, is 0.09 and the yield of formaldehyde, the major product of the direct charge transfer reaction, is 0.05 in 1 M ethylene glycol. The quantum yields for these major products, as well as minor products, such as glycolaldehyde and succinaldehyde, have been determined at several concentrations of ethylene glycol and iron. A detailed reaction scheme for the photolysis has been developed.