Essential oils artificial esters

Bodies of an alcholic nature play a very important part in both natural and synthetic perfumery. They are found to a very large extent in essential oils, both in the free state and also in the form of esters. Some that have not so far been recognised as constituents of essential oils, have been found to be so highly odorous, and so useful as perfume materials, that they are prepared artificially, and enter largely into the composition of the synthetic perfumes which to-day are indispensable to the manufacturer of perfumes. It is obvious that those alcohols which are soluble in water, such as methyl and ethyl alcohols, although they may be original constituents of some essential oils, are removed by the ordinary distillation processes, so that they do not, in fact, appear in the essential oil as found in commerce. 

The esters belonging to the geraniol series of alcohols are absolutely indispensable in the manufacture of artificial perfumes. When it is remembered that these esters are present in such oils as bergamot, rose, geranium, lavender, petit-grain, neroli, and numerous other sweetsmelling essential oils, it will readily be seen how useful they are in building up similar perfumes artificially. 

The Detection of Artificial Esters in Essential Oils.—The custom of valuing certain essential oils, such as lavender, bergamot, geranium, petit-grain, etc., by the determination of their ester-content, has led to the use of scientific adulterants in the form of artificial esters which have been deliberately employed for the purpose of misleading the analyst. Of course, the ester determination is not a true criterion of value, as most of this class of oUs owe their perfume value to various other bodies as well. The first compounds of this nature employed for adulteration were ethyl succinate and ethyl oxalate. For the detection of these in lavender oil the foUowing test was proposed by Guildemeister and Hoffman —... 

Esters.— The simplest class of compounds present in essential oils are the esters or ethereal salts (p. 140). In our early discussion of these compounds in the aliphatic series it was stated that the odor and flavor of common fruits is probably due to ester compounds and that certain empirical mixtures of esters are used as artificial fruit essences. Artificial apple essence, for example, may be prepared by mixing certain proportions of ethyl nitrite, ethyl acetate and amyl valerate with chloroform, aldehyde and alcohol. An example of an essential oil which consists of a single ester is oil of wintergreen. vAdxh is the methyl ester of salicylic acid, ortho-hydroxy benzoic acid (p. 714). 

Essential oils are volatile substances and chemically different from the fatty oils. Their characteristic compounds are monoterpenes and esters with short-chain fatty acids. There are about 2500 essential oils but only about 100 are used. The essential oils are used especially in the perfume industry and for cosmetic articles in the food industry for creating aromatic essences in plastics, artificial leather, rubber, floor wax, household sprays and in pharmaceutical preparations because of their pharmaceutical effects, their antiseptic properties, and to improve taste. 

Esters are among the most important of the carboxylic acid (and alcohol) derivatives. Substances possessing this functional group are widely distributed in nature in the form of waxes, essential oils, fatty acid esters, and aromas. The ester functionality plays a significant role in biochemistry, both in primary metabolism and in a variety of substances exhibiting remarkable physiological activity in humans (hormones and neurotransmitters). Esters find extensive use in commercial products from fingernail polish remover and artificial sweeteners, to polymeric fibers, plasticizers, and surfactants. 

Benzyl Acetate.—This ester is a constituent of the oils of jasmin, ylang-ylang, and similar flower oils. It has not a very intense odour, but is essential to the successful production of such perfumes as artificial jasmin. It has the formula CgHg, CH2. O. OCCH3. It is a colourless oU, boiling at 206° at ordinary pressure, and has a specific gravity 1-0570 at 16° and a refractive index 1-5034 . The propionic ester has the formula C0H5CH2OOCCH2CH3, and closely resembles the acetate in odour. 

---