Novel hydroperoxides as primary autoxidation products of a model ethoxylated surfactant

Ethoxylated alcohols, widely used as surfactants, are susceptible to oxidation when exposed to air. A complex mixture is formed, in which alkylated aldehydes, alkylated formates, hydroxyaldehydes, and formaldehyde have previously been identified by our group. The compounds identified so far are all secondary oxidation products, some of which have been shown to be skin sensitizers and irritants. The primary oxidation products from ethoxylated surfactants have been described as peroxides and hydroperoxides, but their structures have not been elucidated more closely. Hydroperoxides are reactive species and can be suspected to be biologically active as skin sensitizers and irritants. In the present study we used a small model compound, diethyleneglycol monoethylether (C2E2), to facilitate the identification of primary oxidation products formed at autoxidation of ethoxylated surfactants. By performing NMR and HPLC-MS analyses, we found that at least four different hydroperoxides were formed at autoxidation of C2E2, one of them dominating in concentration over the others. The hydroperoxide present in the highest concentration was identified as 2-[2-(1-hydroperoxyethoxy)ethoxy]ethanol.