6-Nonenal is an organic compound with the formula C2H5CH=CH(CH2)4CHO. Other isomeric nonenal compounds are also known to exist naturally, e.g. 2-nonenal. The cis-isomer of 6-nonenal is often listed as the principal component in the aromas of muskmelon fruits.[1] The trans-isomer is listed as an off-flavor aroma of milk foams,[2] and thought to be a possible polypropylene odorant.[3]
 cis-6-Nonenal
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 trans-6-Nonenal
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| Names | |
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| IUPAC names
(Z)-Non-6-enal
(E)-Non-6-enal | |
| Other names
6-Nonenal
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C9H16O | |
| Molar mass | 140.226 g·mol−1 |
| Appearance | Colorless liquid |
| Density | 0.841 g/cm3 |
| Boiling point | 62 to 63 °C (144 to 145 °F; 335 to 336 K) at 2 mmHg |
| Solubility in water | 0.63 g/L |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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Irritant |
| Flash point | 113 °C (235 °F; 386 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Biosynthesis
edit6-Nonenal is thought to be biosynthesized from γ-lineolenic acid catalyzed by a lipoxygenase. The lipoxygenase converts alkene groups into hydroperoxides, which cleave by hydroperoxide lyase into the corresponding cis-aldehydes.[4] Consistent with this mechanism, the odor of muskmelons requires exposure to air. In the ripe, unmodified muskmelon, cis-6-nonenal exists in only low concentration. A steep increase in the concentration of 6-nonenal is noticed when the cells are lysed and exposed to air. This increase is attributed to rapid formation of hydroperoxides. Trans,cis-2,6-nonadienal is a related fragrance that arises via a similar pathway.
Laboratory synthesis
editEither geometric isomer of this compound may be prepared by preparing by brominating 5-octene-1-ol, then preparing the appropriate Grignard reagent. Triethyl orthoformate is treated with this Grignard reagent, then hydrolyzed to give 6-nonenal.[5]
References
edit- ^ Hong, S.J.; Lee, S.K.; Oh, S.H. (2011). "Aroma Volatile Changes of Netted Muskmelon (Cucumis melo L.) Fruit during Developmental Stages". J. Hort. Environ. Biotechnol. 52 (6): 590–595. doi:10.1007/s13580-011-0090-z. S2CID 44969740.
- ^ Allen, C.A.; Parks, O.W.; Schwartz, D.P.; Wong, N.P. (1969). "6-trans-Nonenal: an off-flavor component of foam spray-dried milks". Journal of Dairy Science. 52 (7): 953–956. doi:10.3168/jds.S0022-0302(69)86673-7.
- ^ Haar, N.; Hopfer, H.; Leitner, E.; Sauer, C.; Stockreiter, W. (2012). "Combining different analytical approaches to identify odor formation mechanisms in polyethylene and polypropylene". J. Anal. Bioanal. Chem. 402 (2): 903–919. doi:10.1007/s00216-011-5463-8. PMID 22048233. S2CID 23691565.
- ^ Harada, T.; Hatanaka, A.; Kajiwara, T. (1975). "Biosynthetic Pathway of Cucumber Alcohol: trans-2,cis-6-nonadienol via cis-3,cis-6-nonadienal". Phytochemistry. 14 (12): 2589–2592. Bibcode:1975PChem..14.2589H. doi:10.1016/0031-9422(75)85230-7.
- ^ Seifert, R.M. (1981). "Synthesis, Spectra, Odor Properties, and Structural Relationship of (Z)-6-Nonenal and (Z)-5-Octen-l-ol to Fruit Fly Attractants". J. Agric. Food Chem. 29 (3): 647–649. doi:10.1021/jf00105a053.