Fragrance industry

Several Diels-Alder reactions in which acrolein participates as the dienophile are of industrial significance. These reactions involve butadiene or substituted butadienes and yield the corresponding 1,2,5,6-tetrahydroben2aldehyde derivative (THBA) examples are given in Table 9 (90). These products have found use in the epoxy and perfume/fragrance industries. 

A commercially important outlet in the fragrance industry is the methyl dihydrojasmonate [24851-98-7] (26) which is made by Michael addition of a malonate to 2-pentyl-2-cyclopenten-l-one [91791 -21 -8] (52) and which is used in perfumery for blossom fragrances, particularly jasmine (see Perfumes). 

Rose. Of all the natural oils, rose is probably the most desired material used in the fine fragrance industry. For years chemists have tried to unravel the mystery of the odor-donating components of this high priced natural material. Simple glc analysis shows that nine components constitute nearly 89% of the total volatiles of rose otto (9) (see Table 2). 

Essential Oils. Essential oils are produced by distillation of flowers, leaves, stems, wood, herbs, roots, etc. Distillations can be done directly or with steam. The technique used depends mosdy on the desired constituents of the starting material. Particular care must be taken in such operations so that undesired odors are not introduced as a result of pyrolytic reactions. This is a unique aspect of distillation processing in the flavor and fragrance industry. In some cases, essential oils are obtained by direct expression of certain fmits, particular of the citms family. These materials maybe used as such or as distillation fractions from them (see Oils, essential). 

Another analysis handled effectively by use of gc/ir/ms is essential oil characterization which is of interest to the foods, flavors, and fragrances industries (see Oils essential). Even very minor components in these complex mixtures can affect taste and aroma. Figure 4 shows the TRC and TIC for Russian corriander oil which is used extensively in seasonings and perfumes (15). The ir and ms are serially configured. Spectra can be obtained from even the very minor gc peaks representing nanogram quantities in the it flow cell. 

Capillary gc/ms, hplc, nmr, ir, and uv are all analytical methods used by the terpene chemist with a good Hbrary of reference spectra, capillary gc/ms is probably the most important method used in dealing with the more volatile terpenes used in the davor and fragrance industry (see Flavors and spices). The physical properties of density, refractive index, boiling point, melting point of derivatives, and specific rotation are used less frequendy but are important in defining product specifications. 

Dimerization of Isoprene. Isoprene is becoming an increasingly important raw material for the production of terpenes. For example, myrcene (7) can be produced by the dimerization of isoprene (2-methyl-1,3-butadiene) (42—44) and myrcene is very useful for synthesizing a number of oxygenated terpenes important in the flavor and fragrance industry. 

In flavor formulations, vanillin is used widely either as a sweetener or as a flavor enhancer, not only in imitation vanilla flavor, but also in butter, chocolate, and aU. types of fmit flavors, root beer, cream soda, etc. It is widely acceptable at different concentrations 50—1000 ppm is quite normal in these types of finished products. Concentrations up to 20,000 ppm, ie, one part in fifty parts of finished goods, are also used for direct consumption such as toppings and icings. Ice cream and chocolate are among the largest outlets for vanillin in the food and confectionery industries, and their consumption is many times greater than that of the perfume and fragrance industry. 

In the 1990s hplc has become widely used in the flavor and fragrance industry to measure vanillin and other phenoHc compounds. Routine methods have been developed that are particularly adapted to thermosensitive products, such as vanillin and its derivative products, with elution gradient and uv detection at given wavelengths. Certain critical impurities can thus routinely be traced to very low (10 ppm) concentrations. 

Replacement of organic solvents by water may be done for environmental, cost e.g. reduction in raw materials and VOC containment costs) or technical reasons. In the flavour and fragrance industry, where the presence of even trace amounts of volatile impurities can be detected by the expert nose , significant process costs are entailed in ensuring complete removal of solvent. If reactions can be carried out in water then these additional costs can be saved. As an example geraniol can be isomerized to the important fragrance intermediates a-terpinol and linalol in water at 220 °C (Scheme 5.9). 

Plants produce a vast array of terpenes, alkenes built in multiples of five carbon atoms. Many terpenes have characteristic fragrances. For example, the fresh odor of a pine forest is due to pinene, a ten-carbon molecule with a ring structure and one double bond. The fragrances of terpenes make them important in the flavor and fragrance industry. Limonene, another ten-carbon molecule with a ring and two double bonds, is the principal component of lemon oil. Geraniol, a chainlike molecule with two double bonds, is one of the molecules that is responsible for the fragrance of roses and is used in many perfumes. Many other terpenes have important medicinal properties. 

The enantioselective hydrogenation of a,fj- or / ,y-unsaturated acid derivatives and ester substrates including itaconic acids, acrylic acid derivatives, buteno-lides, and dehydrojasmonates, is a practical and efficient methodology for accessing, amongst others, chiral acids, chiral a-hydroxy acids, chiral lactones and chiral amides. These are of particular importance across the pharmaceutical and the flavors and fragrances industries. 

Analytical balances, 26 245 Analytical chemistry. See also Analytical methods/techniques in the fragrance industry, 13 379-381 of manganese compounds, 15 611-613 organic titanium compounds in, 25 135 of plutonium, 19 699-700 of thorium, 24 774... 

Enantioselective heterogeneous catalytic reactions are of growing interest, as optically pure chiral compounds are of great importance in different areas like fine chemical, pharmaceutical, agrochemical, flavor, and fragrance industries. 

The fragrance industry is closely linked to the flavour industry. Many of the skills required of a perfumer are also required of a flavourist. Find out more about the flavour industry. Contact the chemistry department of a university to find out more about flavour chemistry. 

There is currently great interest in the flavor and fragrance industry in developing natural chiral chemicals from plant materials. The interest in natural chiral chemicals continues to grow for several reasons ... 

An example of commercial interest is the synthesis of citronitrile (Scheme 17), a compound with a citrus-like odor, which is used in the cosmetics and fragrance industries. The first step in the synthesis of citronitrile is the Knoevenagel condensation of benzyl acetone and ethyl cyanoacetate. This condensation has been carried out with MgO and Al-Mg calcined hydrotalcites as catalysts (148). Similar results were obtained with the two solid catalysts, with yields of 75% of the Knoevenagel adduct. 

The biosynthesis of geosmin is of interest because an enhanced understanding of the pathways and enzymes involved may support the development of effective off-flavor control strategies. Increased biochemical information could also enhance the use of biochemical systems to produce large amounts of geosmin for the flavor and fragrance industries, which may be interested in this compound to provide a desirable earthy note to certain products (88). Currently, difficulties associated with the synthesis of the three chiral carbons renders the chemical synthesis of geosmin extremely difficult (88). 

Naturally occurring fatty alcohols used in the fragrance industry are produced principally by reduction of the methyl esters of the corresponding carboxylic acids, which are obtained by transesterification of natural fats and oils with methanol. Industrial reduction processes include catalytic hydrogenation in the presence of copper-chromium oxide catalysts (Adkins catalysts) and reduction with sodium (Bouveault—Blanc reduction). Unsaturated alcohols can also be prepared by the latter method. Numerous alcohols used in flavor compositions are, meantime, produced by biotechnological processes [11]. Alcohols are starting materials for aldehydes and esters. 

Currently, raw materials for the flavor and fragrance industry are obtained from more than 250 different plant species, but only a handful of products originate... 

The flavor and fragrance industry has expanded so much that the plants required to supply the raw materials are now grown on a very large scale. Examples are the peppermint and spearmint plantations in the United States, the lavandin plantations in southern France and the cornmint plantations in China and India. 

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