Structure-Odor Relationships of ( Z)-3-Alken-1-ols, ( Z)-3-Alkenals, and ( Z)-3-Alkenoic Acids.

( Z)-3-Unsaturated volatile acids, alcohols, and aldehydes are commonly found in foods and other natural sources, playing a vital role in the attractiveness of foods but also as compounds with chemocommunicative function in entomology. However, a systematic investigation of their smell properties, especially regarding humans, has not been carried out until today. To close this gap, the odor thresholds in air and odor qualities of homologous series of ( Z)-3-alken-1-ols, ( Z)-3-alkenals, and ( Z)-3-alkenoic acids were determined by gas chromatography-olfactometry. It was found that the odor qualities in the series of the ( Z)-3-alken-1-ols and ( Z)-3-alkenals changed, with increasing chain length, from grassy, green to an overall fatty and citrus-like, soapy character. On the other hand, the odor qualities of the ( Z)-3-alkenoic acids changed successively from cheesy, sweaty via plastic-like, to waxy in their homologous series. With regard to their odor potencies, the lowest thresholds in air were found for ( Z)-3-hexenal, ( Z)-3-octenoic acid, and ( Z)-3-octenal.