Fragrance and Flavor Chemicals

The role of fragrances since ancient times has been to cover unpleasant smell and to provide a pleasing impression (e.g., fmity, floral, marine etc.). Fragrance and flavor raw materials are obtained either from natural sources (e.g., terpenes, plant essential oils, animal secretions or from chemical synthesis. As the enantiomers of many odorant molecules differ in strength and in odor/taste description, the selective (and often catalytic) synthesis of the more appreciated isomer is of great interest. This avoids the dilution effect by the non-desired isomer and reduces the amount of active ingredient in the final product. Table 5.3.19 shows the example of (Sj-citronellol, an important perfumery raw material with a rose note. 

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The number of synthetically produced fragrance and flavor chemicals has since expanded continually as a result of the systematic investigation of essential oils and fragrance complexes for odoriferous compounds. Initially, only major components were isolated from natural products their structure was then elucidated and processes were developed for their isolation or synthesis. With the development of modern analytical techniques, however, it became possible to isolate and identify... 

Among the acyclic terpene aldehydes, citral and citronellal hold key positions as fragrance and flavor chemicals, as well as starting materials for the synthesis of other terpenoids. Hydroxydihydrocitronellal is one of the most important fragrance materials. Derivatives of these aldehydes, particularly the lower acetals, are also used as fragrance materials. Acyclic sesquiterpene aldehydes are not very important as such, but they contribute to the characteristic fragrance and aroma of essential oils, for example, in the case of a- and /3-sinensal in sweet orange oil. 

R = CH3, C9H10O2, Mt 150.18, fepiookPa 215 °C, 4° 1.0550, reg1 1.5232, is the main component of jasmine absolute and gardenia oils. It occurs as a minor component in a large number of other essential oils and extracts. It is a colorless liquid with a strong, fruity, jasmine odor. Benzyl acetate is prepared by esterification of benzyl alcohol with acetic anhydride (e.g., with sodium acetate as a catalyst) or by reaction of benzyl chloride with sodium acetate. In terms of volume, benzyl acetate is one of the most important fragrance and flavor chemicals. 

Figure 10. Synthesis of some fragrance and flavor chemicals from 6-pinene.

Albert, R. M., Traynor, S. G. Webb, R. L Fragrance and Flavor Chemicals, in Naval Stores - Production, Chemistry, Utilization, D. F. Zinkel and J. Russell (eds.), Pulp Chemicals Association, New York 1989. 

Others. Safrole present in sassafras oil is used as a starting material for the synthesis of heliotropin (piperonal), an important fragrance and flavor chemical. 

Enantiomerically pure citronellal in both of its antipodal forms has outstanding importance as a key intermediate for the production of fine chemicals, especially for the production of fragrances and flavors. In this respect the isomerization of diethylgeranylamine to R) -citronellal enamine in the presence of Rh /(S) -BINAP is an exceptional industrial process, for instance as one of the key steps of the Takasago process for the production of (-) -menthol [22]. In the search for alternatives for this process, both Josiphos and Daniphos derivatives were evaluated (Scheme 1.4.5) [23]. 

Since early antiquity, spices and resins from animal and plant sources have been used extensively for perfumery and flavor purposes, and to a lesser extent for their observed or presumed preservative properties. Fragrance and flavor materials vary from highly complex mixtures to single chemicals. Their history began when people discovered that components characteristic of the aroma of natural products could be enriched by simple methods. Recipes for extraction with olive oil and for distillation have survived from pre-Christian times to this day. 

What these companies sell are fragrance and flavor materials. They are not illegal. They are not watched. The industry is not policed. But let me qualify this. Yes, some of the companies that sell essential oils and extracts also make aromatic chemicals. And, yes, some of those chemicals are watched or restricted. It is the nature of the industry that some chemicals of this type are included in the product list of some companies. Even watched/restricted chemicals have uses in this world so people are gonna sell them. 

Though there are hundreds of companies engaged in the business of aroma chemicals, it is strange that the top eight full service companies—manufacturers in all three categories of flavors, fragrances, and aroma chemicals—enjoy two-thirds of the World s total business. A few hundred small companies account for only one-third of the business. 

The outcome is a report that will hopefully be truly useful to heads of chemical research as well as to managers in the fine chemical, fragrance and flavor, pharmaceutical, and polymer industries for years to come. 

The manufacture of fine chemicals, particularly drugs, fragrances, and flavors, is undergoing a major revolution now as a result of the capability of chemists to prepare these chemicals, mainly drugs, in their purest isomeric forms (as stereoisomers). This shift to pure forms has been described by Brown in the following words (1990) (see also Deutsch, 1991) A mixture of stereoisomers in a medicine will (now) need to be justified just the same way as any other mixture of compounds. Indeed, in the United States today (as in many other advanced countries), the use of pure enantiomeric forms is practically a requirement since extensive justification is needed to continue with racemates (FDA, 1992). As a consequence, the combined sales of the chiral top ten drugs (ammoxydllin, enalapril, ampicillin, captopril, pravastatine, diltiazem, ibuprofen, lovastatin, naproxen, and fluoxetine) in 1994 amounted to more than 16 billion dollars (Sheldon, 1996). (Of these, ibuprofen and fluoxetine are still sold as racemates.)... 

The rapid development of the fragrance and flavor industry in the nineteenth century was generally based on essential oils and related natural products. In 1876, however, Haarman and Refiner started the first production of synthetic aroma chemicals—vanillin, then coumarin, anisaldehyde, heliotropin, and terpineol. Although aroma chemicals made a revolution in fragrances with top discoveries in the twentieth century, for many decades both flavors and fragrances were manufactured with constituents of natural origin, the majority of which were essential oils. 

This CoP is complementing the information of IFRA and lOFI. It is continuously updated by experts of the industry and the trade by the Hazard Communication Working Group (HCWG) and furnishes for the disposal of people all over the world occupied in handling essential oils and aromatic chemicals an up-to-date recommendation for a proper classification and labeling of hazardous fragrance and flavor raw materials (Protzen, 1989). 

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