Emission from the species CH3COC(OH)2CH3 in aqueous solutions of biacetyl

A previously unreported emission at 435 nm from solutions of biacetyl in water, methanol or ethanol has been observed. It results from excitation at the 280 nm absorption peak but not from excitation at the 405 nm absorption maximum; its intensity is proportional to the amount of water/acetonitrile mixtures, and is insensitive to air concentration. Comparison of the position and intensity of this new peak with the fluorescence maxima of simple ketones such as acetone suggest that it is emission from biacetyl hemi-hydrate or hemiketal, known to be the predominant species in aqueous solutions of biacetyl, and shown to be the predominant species in alcoholic solutions.