Floral odours

Benzylidene acetone, C Hg. CH CH. COCH, is a crystalline body melting at 42°, having an intense floral odour. It restilts from the condensation of benzaldehyde and acetone under the influence of caustic soda. It has the following characters —... 

Patt, J. M Hartman, T. G., Creekmore, R. W. et al. (1992). The floral odour of Peltandra virginica contains novel trimethyl-2,5-dioxabicyclo[3.2.1.]nonanes. Phytochemistry 31 487-491. 

Tollsten, L. and Bergstrom, L.G. (1989). Variation and post-pollination changes in floral odours released by Platanthera bifolia (Orchidaceae). Nordic Journal of Botany 9 359-362. 

In black pepper, caryophyllene-rich oils possess sweet floral odours, whereas oils... 

The essential oil is a pale yellow with a light, bitter-sweet floral odour. The absolute is darker and more viscous with an odour closer to the original flower. The main chemical components of the essential oil are the alcohol lin-alool (30-37%), the ester linalyl acetate (6-17%) and monoterpenes limonene (12-18%) and [3-pinene (12-15%). Also present geraniol (2-3%), nerol (1-3%), nerolidol (3-6%), citral and jasmone. Both the plant and the essential oil have many established uses. The essential oil is considered to be one of the most effective as a sedative, carmative and antidepressant and often used to treat insomnia. It is also claimed to be relaxant for smooth muscle (internal, involuntary muscles) especially those of the gut. Suitable for all skin types, both the essential oil and hydrolat are versatile materials for the aromatherapist. Considered safe as it is nonirritant and non-sensitizing and an example of a non-phototoxic citrus essential oil. 

The Fischer indole synthesis is a versatile method for preparing 2,3-substituted indoles. Indoles itself, in small concentrations, has a floral odour while many of 2,3-substituted indoles are biologically active and also find applications as pharmaceuticals and plant growth regulators. 

Concerning the impact of ethanol on aroma perception, Pet ka et al. (2003) showed that ethanol at low concentrations (under 10%) could decrease aroma compound detection threshold. Nevertheless, Grosch (2001) observed that the less ethanol present in a complex wine model mixture, the greater the intensity of the fruity and floral odours. Although this effect could be easily explained by the increased partial pressure of the odorants with reduced ethanol concentration, they showed in GC-0 (gas chromatography-olfactometry) experiments that ethanol strongly increased the odour threshold of wine volatiles. In fact the reduction in odour activity of the wine volatiles when ethanol was added was much larger than the reduction in their partial pressure. 

Among the odorants listed in Table 6.33, l-octen-3-ol (no. 4), the character impact aroma compound of mushrooms [62], is also responsible for the characteristic mush-room-like note of camembert, which is intensified by l-octen-3-one (no. 5). Although the concentration of this ketone is much lower than that of the alcohol, it can be aroma-active in cheese because its odour threshold is 100 times lower than that of the alcohol [60], Methanethiol, methional, dimethylsulphide, dimethyl trisulphide and methylene-bis(methylsulphide) generate the sulphurous odour note, whereas phenyle-thyl acetate is responsible for the floral odour note [61 ]. 

The damascones are a group of materials related to the ionones, but in which the enone unit is transposed. They are components of rose oils and have very intense fruity-floral odours. The damascenones, which contain a second double bond in the ring, are also very much sought after. One synthesis of a-damascone from methyl a-cyclogeranate is shown in Scheme 4.40. A double Grignard addition gives the tertiary alcohol. Heating of this in the presence of base, to prevent elimination... 

Acetylation of naphthalene gives methyl naphthyl ketone, and sulfonation followed by alkaline fusion gives naphthol (Scheme 4.60). The methyl and ethyl ethers of naphthol are prepared from naphthol by reaction with the corresponding alkyl sulfate under basic conditions. These ethers are usually known by the shorter names of yara and nerolin, respectively. Yara, nerolin and methyl naphthyl ketone possess floral odours and are moderately important perfume ingredients. 

Cyclopentanone readily undergoes aldol condensation with a variety of aldehydes to give the 2-alkylidenecyclopentanones (Scheme 4.66). These have jasmine-like odours, but are no longer used in perfumery since it was discovered that they have the potential to cause skin sensitization. The saturated products are safe and are used to give jasminic, fruity, floral odours in fragrances. The most widely used are the H-heptyl- (R = pentyl) and -hexyl- (R = butyl) derivatives. These are sold under tradenames such as Heptone and Jasmatone , respectively. 

Since the blossom oil of lily of the valley is not commercially available, the perfumers have to rely on synthetic substitutes, such as hydroxy-citronellal (1), Lilial (3) and Bourgeonal (6) to create their muguet fragrances. The oldest lily of the valley odorants, hydroxycitronellal and cyclamen aldehyde (2) (Winthrop Chem. Corp., 1929), were discovered by chance. Serendipity still continues to play an important role. Anselmi et al. (1992) synthesized and organoleptically screened a series of 38 tetrahydropyranyl ethers. This class of compounds was chosen because of their ease of synthesis and purification, and because of their stability in alkaline media, conditions under which aldehydes tend to undergo aldol condensations. Two compounds (24 and 25) were described as having a white, floral odour reminiscent of hydroxycitro-... 

Another example of analogue synthesis dates back to the 1960s. As mentioned above, the first phenylpropanal to be discovered with a white, floral odour was cyclamen aldehyde, 3-(4-isopropylphenyl)-2-methylpropanal (2). As the name implies, its odour is reminiscent of wild cyclamen. However, at low concentrations the odour possesses a hydroxycitronellal-like note. Consequently, it was common practice in the 1960s to replace hydroxycitronellal, which is unstable in alkaline media and irritating to the skin, with cyclamen aldehyde. However, from an odour point of view the substitution was not entirely satisfactory. The discovery of the closely related r-butyl analogues (3 and 6) resulted in a certain improvement (Givaudan Corp., 1959 Boelens and Wobben, 1980). Both of these compounds have a more pronounced muguet floral odour. 

Long rectangular prisms with faint floral odour (EtOH or AcOH). Mp 87-88°. 

R3 iH and R3GeH can be electrochemically halogenated in MeCN and catalytically (Rh) reduce alkynes, GeH4 adds to (CP3)2CO, while PhMeGe(H)C H20Ac shows sweet-floral odour and is thermally more stable than the analogous silane ... 

Camembert-type cheeses with a powdery rind of white mold Penkillium camemberti) smeU pleasantly of mushrooms, earth and garlic. The characteristic component of the mushroom-like odour is oct-l-en-3-ol, the floral odour components are primarily 2-phenylethanol and 2-phenylethyl acetate, and 1,3-dimethoxybenzene and methyl cinnamate are responsible for the odour resembling nuts. The garlic note of matured cheese is caused by the presence of sulfur compounds, such as 2-bis (methylthio)methane, also known as bis(dimethylsulfanyl)-methane or 2,4-dithiapentane, tris(methylthio) methane, also known as tris(methylsulfanyl)methane or 3-methylthio-2,4-dithiapentane, methyl (methylthio)methyl disulfide, also known as (methyldisuflanyl) methylsulfanylmethane or 2,3,5-trithiahexane, and bis(methylthiomethyl) sulfide (8-186). 

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