Alcohol in the flavor and fragrance

The principal industrial appHcation for isobutyl alcohol is as a direct solvent replacement for 1-butanol. It is also used as a process solvent in the flavor and fragrance, pharmaceutical, and pesticide industries. The maximum employment of isobutyl alcohol was in the mid-1980s when it had a distinct price advantage over 1-butanol (10). More recently, however, with increased demand for other value added derivatives of isobutyraldehyde, the price differential between isobutyl and -butyl alcohols has diminished resulting in a switching back by some consumers to 1-butanol. 

The history of monohydric alcohol-based ester-type plasticizers for polyvinyl chloride is reviewed, and a prediction of the future for these plasticizers in the eighties is made. Finally, although not in the large volume category compared to many monohydric alcohols, the rather sophisticated chemistry used to produce monohydric alcohols for the flavors and fragrance industry is covered. 

Nor has nature neglected to bless fruits with alcohols which add their special touch to the flavors of fresh fruit. A list of alcohols found in apple and banana extracts is shown in Figure 4. These examples suffice to show how widely distributed alcohols are in natural flavors and fragrances. 

The Ci5 terpenoids known as sesquiterpenoids are the most chemically diverse group of terpenoids known in nature. Like monoterpenoids, many sesquiterpenoids contribute to the flavor and fragrances of a variety of plant products. To date about 10,000 sesquiterpenoids are known (32), and in the plant kingdom they commonly occur as hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, lactones, and oxiranes. The acyclic sesquiterpene hydrocarbons a- and p-farnesenes (HI and H2, respectively) (Fig. 8) are constituents of the oils... 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

Pyrolytic Decomposition. The pyrolytic decomposition at 350—460°C of castor oil or the methyl ester of ricinoleic acid spHts the ricinoleate molecule at the hydroxyl group forming heptaldehyde and undecylenic acids. Heptaldehyde, used in the manufacture of synthetic flavors and fragrances (see Elavors and spices Perfumes) may also be converted to heptanoic acid by various oxidation techniques and to heptyl alcohol by catalytic hydrogenation. When heptaldehyde reacts with benzaldehyde, amyl cinnamic aldehyde is produced (see Cinnamic acid, cinnamaldehyde, and cinnamyl... 

Esters of araliphatic alcohols and aliphatic acids are interesting as flavors and fragrances because of their characteristic odor properties. Acetates are the most popular esters. Benzyl acetate is particularly important commercially and occupies a prominent position in the fragrance and flavor industry. 

Health and Safety. This material has a Generally Recognized As Safe (GRAS) status indicated by the Flavor and Extract Manufacturers Association for use in flavors and by the Council of Europe for use as a flavor. Benzyl alcohol satisfies the most current guidelines published by (lie International Fragrance Association (IFRA) which governs the use of fragrance materials. 

Givaudan Corporation, probably the largest supplier of flavor and fragrance chemicals, offers about 50 monohydric alcohols. This is by no means the whole picture. Other suppliers offer additional alcohols and some alcohols are used in-house as intermediates,... 

In certain cases it is desirable to selectively remove a volatile solute from a solution that contains other, less volatile, solutes as well as the solvent. Some examples are the reduction of ethanol content from alcoholic beverages or from dilute alcoholic extracts of aromatic flavors and fragrances from plant sources such as fruits or flowers. Conventional pervaporation would facilitate removal of water from such mixtures while retaining ethanol and the higher molecular weight organics that comprise the characteristic aroma and flavor profile of the products of interest. On the other hand, membrane distillation or osmotic distillation cannot retain the volatile components at all. 

Alcohols occur widely in nature. Methanol is also known as wood alcohol because it can be obtained by distilling wood in the absence of air. It is very poisonous and can cause blindness or death if ingested. Ethanol is consumed in alcoholic beverages. Other simple alcohols, such as 2-phenylethanol from roses and menthol from peppermint, are constituents of natural flavors and fragrances. Alcohols are important intermediates in chemical synthesis. They are also commonly used as solvents for various chemical processes. Ethylene glycol is used in antifreeze and in the preparation of polymers such as Dacron. 

For example, hydrogenation of a- and/or / -pinene, over nickel or palladium catalysts, affords ds-pinane. Autoxidation of ds-pinane (in the absence of a catalyst) gives the tertiary hydroperoxide (see Fig. 8.42) which is hydrogenated to the corresponding alcohol. Thermal rearrangement of the latter affords the important flavor and fragrance and vitamin A intermediate, linalool (Fig. 8.42) [213]. 

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