Identification and Persistence of 5,6-Dihydro-2-pyran-3-carboxaldehyde in Aged Aqueous Acrolein Media.

Acrolein hydrolysis byproducts are a part of good industrial stewardship practice. Aqueous acrolein is used worldwide as an industrial raw material, an herbicide, an oilfield biocide, a hydrogen sulfide scavenger, and a molluscicide. Industrial acrolein is obtained by the catalytic oxidation of propylene followed by aqueous absorption and then by distillations. Generally, the fate of aqueous acrolein is described as occurring by hydrolysis, evaporation, absorption into the ground, and its consumption by the intended application purposes and conditions. Measurements of acrolein in water are normally confined to its loss. However, its byproducts are rarely discussed. In this study, an aged acrolein solution has been found to contain byproduct aldehydes, including the major soluble 5,6-dihydro-2-pyran-3-carboxaldehyde. Despite acrolein's facile hydrolysis degradation, this byproduct is surprisingly stable in aqueous media for at least 25 years at ambient temperatures. The presence of this byproduct has been established by H and C NMR, using DEPT, COSY, and HMBC, and UV spectroscopy at λ 229 nm in natural water systems.