Characterization of Odor-Active 2-Ethyldimethyl-1,3,6-trioxocane Isomers in Polyurethane Materials

Polyurethane materials, widely used in indoor environments, occasionally exhibit unpleasant odors. An important source of polyurethane odorants is polyether polyols. Previous studies identified odorous 2-ethyldimethyl-1,3,6-trioxocanes in polyurethane materials and polyols but did not investigate the odor activity of the individual isomers. In the present work, an isomer mixture of the precursor dipropylene glycol was fractionated through preparative high-performance liquid chromatography. After the conversion to the corresponding trioxocanes, gas chromatography-olfactometry analyses revealed that just one positional isomer, namely 2-ethyl-4,7-dimethyl-1,3,6-trioxocane, was odor active. Moreover, we observed clear differences in the odor threshold concentrations among its stereoisomers. Only two out of eight isomers displayed an odor, both with an earthy smell and one being approximately 60 times more potent than the other. These insights contribute to a better understanding of polyurethane odor on a molecular level and provide a basis for effective odor control.