trans-2,cis-6-Nonadienal-D5 is a labelled analogue of trans-2,cis-6-Nonadienal (N649365). trans-2,cis-6-Nonadienal is an unsaturated aldehyde that is responsible for the cucumber smell of Synura petersenii, a freshwater colonial flagellate. trans-2,cis-6-Nonadienal is also a common natural and drinking water contaminant.