Nona-2,6-dienal

Hence the compound is nona-2,6-dienal. The relative configuration of both CC double bonds follows from the HH coupling constants of the alkene protons in the H NMR spectrum. The protons of the polarised 2,3-double bond are in trans positions Jhh 5.5 Hz) and those on the 6,7-double bond are in cis positions Jhh = 10.5 Hz). The structure is therefore nom.-2-tmns-6-cis-dienal, D. 

E, <()-Nona-2,6-dienal Cucumis satirns (Cucurbitaceae), JVephelium OD-R (green, cucumber,... 

Trace components are often important and may contribute more significantly to the flavor than major ones. In lemon, for example, limonene (11) makes up about 70% of the oil, but it is the content of citral, a mixture of geranial (61) and neral (60) (less than 5% of the oil), that produces the lemon flavor. An even more effective example is that of cucumber smell produced by nona-2,6-dienal. This substance has an odor threshold of 0.0001 ppm (Harbome, 1982). 

E,6Z)-Nona-2,6-dienal Cucumber-like Fresh cucumbers... 

Some compounds formed from meat lipids have an important role. Such compounds include some carbonyl compounds, such as oct-l-en-3-one, hexanal, octanal, nonanal, (Z)- and ( )-non-2-enal, (2 ,6Z)-nona-2,6-dienal, (2 ,4Z)-deca-2,4-dienal and 12-methyltridecanal (8-181). Other important fatty acid oxidation products include ( )-4,5-epoxydec-2-enal (8-182), (Z)-octa-l,5-dien-3-one, (2 ,6Z)-nona-2,6-dienal. Also important... 

Flavour-active components of fresh fish are further oxidation products of unsaturated fatty acids formed by the action of lipoxygenases. Important compounds are mainly alcohols and carbonyl compounds. For example, oxidation of eicosapentaenoic acid via 12-hydroperoxide yields (3Z,6Z)-nona-3,6-dienal, (2E,6Z)-nona-2,6-dienal, (3Z,6Z)-nona-3,6-dien-l-ol, (Z)-octa-l,5-dien-... 

The aroma of apricots (Armeniaca vulgaris, syn. Prunus armeniaca, Rosaceae) is composed of a large number of different substances. Important components are monoterpenic hydrocarbons, alcohols and aldehydes (myrcene, hmonene, p-cymene, terpinolene, a-terpineol, geranial, geraniol and hnalool in particular) and aldehydes with green flavour, such as (Z)-hex-3-enal and acetaldehyde. Other volatile components include products of oxidation of fatty acids, such as (2 ,6Z)-nona-2,6-dienal, (Z)-octa-l,5-dien-3-one, lactones (y-hexalactone, y-octalactone, y-decalactone, y-dodecalactone, 8-decalactone and 8-dodecalactone), carboxylic acids (especially, 2-methylbutanoic and acetic acids) and degradation products of carotenoids, such as P-ionone. 

The aroma of carrots root Daucus carota, Apiaceae) is very complex. It consists of various aldehydes, ketones, mono- and sesquiterpenic hydrocarbons and other compounds. The important hydrocarbons are myrcene, sabinene, terpinolene, P-caryophyUene, y-bisabolene and a-pinene, which are present in the largest quantities. The significant carbonyl compounds are acetaldehyde and (2 ,6Z)-nona-2,6-dienal. One of the typical aromatic substances determining the basic odour of carrots is 2-sec-butyl-3-methoxypyrazine. During the cooking of carrots, the contents of methanal, ethanal, propanal, octanal, (Z)-dec-2-enal and some sulfur compounds, such as dimethylsulfide and ethanethiol, increase. At the same time, the contents of monoterpenes and P-caryophyUene decrease. 

The key odour-active components of fresh cucumbers Cucumis sativus, Cucurbitaceae) are aldehydes generated by enzymatic oxidation of unsaturated fatty acids. The most important compounds are (3Z,6Z)-nona-3,6-dienal, (2 ,6Z)-nona-2,6-dienal and (Z)-non-3-enal, which recall the smell of fresh cucumbers. Additional important components are some other aldehydes, such as (Z)-hex-3-enal, ( )-hex-2-enal, ( )-non-2-enal, nonanal, (Z)-hex-6-enal, certain alcohols and 2-alkyl-3-methoxypyrazines. 

---