Terpene esters

Essential oils (Section 26 7) Pleasant smelling oils of plants consisting of mixtures of terpenes esters alcohols and other volatile organic substances Ester (Sections 4 1 and 20 1) Compound of the type... 

Coffee oil is generally described as the petroleum ether-soluble fraction from green coffee beans. Arabica coffees contain 11.1 to 13.6% oil, whereas Robusta coffees contain only 4.4 to 4.8% oil.106 Triglycerides constitute 79% of this oil, terpene esters 17%, and the remaining 4% is contributed by sterols, free terpenes, tocopherols, and as yet unknown... 

The GC/MS analysis showed the acetone-insoluble portion to contain hydrocarbons, long-chain aldehydes and alcohols, fatty acids and fatty acid esters while the acetone soluble portion contained terpenes and terpene esters. The yields of the general chemical classes as determined in the analysis of the five samples are summarized in Table III. A high yield of long-chain alcohols (primarily 1-hexacosanol) is found in all the accessions. While the yields are generally comparable in the North American samples, a significantly... 

However, the lower fatty acid esters (particularly the acetates) of the acyclic terpene alcohols geraniol, linalool, and citronellol are extremely important both as fragrance and as flavor substances. The acetates occur in many essential oils, sometimes in rather high amounts. Formates, propionates, and butyrates occur less frequently. As a result of the development of large-scale production processes for terpenes, the esters of acyclic terpene alcohols are nearly always made synthetically. All acyclic terpene esters that are used as fragrance and flavor materials can be prepared by direct esterification of the appropriate alcohols. However, special precautions are required for the esterification of linalool. 

The most important and most frequently used acyclic terpene esters are described below. 

The most important and frequently used terpene esters in flavours are the acetates of nerol, geraniol, citronellol, linalool and isoborneol [12], As discussed before, all these terpene alcohols are available both from renewable resources and from petrochemical origin. Acetic acid can be obtained from renewable resources by pyrolysis of wood as wood vinegar, and also by synthesis from petrochemical origin. 

The thiolester group was used for deracemization of terpenic esters [254]. Racemic 5-phenyl thiocyclogeranate was deprotonated by n-BuLi, and the resulting enolate was protonated by a chiral aminoalcohol, ( )-N-isopropylephedrine. The thiolester was obtained with the highest enantioselectivity (99% e.e.) reported for such a process (carried out on a 40 g scale). With a sulfur group a selective (Z)-enolate was formed and protonation was slower than for esters. 

The emission of a complete set of personal computers and monitors are described by Nakagawa et al. (2003). Several VOC like benzene, toluene, etc. were identified and quantified. The results are shown in Table 17.3. The emission rates of aliphatic hydrocarbons, terpenes, esters, ketones, alcohols and halogens were not found to be significantly different for PCs with CRT and TFT monitors. In the case of aromatic hydrocarbons the emission rates were higher if a PC with CRT monitor was used. The same was found for aldehyde emissions but the differences in emission rates were lower. The separate test CRT monitor and the associated computer in this study proved that the monitor was the main source of chemical emissions. 

Structural formulas of three major natural pyrethrins, which are chemically classified as mono-terpene esters, are given in Figure 19.3. The shaded part of the first structural formula is common to natural pyrethrins, the most characteristic structural feature of which is the cyclopropane group. 

Steam distillation is based on an aceotropic or carrier-gas distillation of two immiscible liquids. Due to the unfavourable ratio of vapour pressures and thus of mole fractions in the distillate, large amounts of water must be evaporated for the separation of small amounts of essential oils. This is connected to long distillation times at around 100°C and a considerable thermal stress leading to the formation of artefacts, oxidation and isomerisation to a certain extent. Moreover the water itself can be a reactant and hydrolyse terpene esters that make up the core of a flavour terpene alcohols remain partially dissolved in the water and thus are lost from the essential oil. All this can modify the essential oil composition and change the original typical flavour impression. 

Use Solvent for protective coatings, polishes, and waxes synthesis of camphene, camphor, geraniol, terpin hydrate, terpineol, synthetic pine oil, terpene esters and ethers, lubricating oil additives, flavoring odorant. 

This enzyme system is also capable of producing certain terpene esters in high yield, for example geranyl butyrate. Furthermore, incubation of toluene solutions of hydroxy acids, such as 4-hydroxy-butyric acid and -hydroxypentadecanoic acid, with the enzyme system, gives rise to the corresponding -butyrolactone and the macrocyclic lactone pentadecanolide. 

This plant is a perennial herb, about one metre in height, endemic to the Balkans (ex.-Yugoslavia) and now grown in many tropical countries, above all, Kenya. Every part of the plant contains pyrethrins, but the highest content is in the flowers, and only these are used. The terpene esters, which have contact-insecticidal effects, are easily decomposed on... 

Ceylon cinnamon oil (1) shows an additional violet-blue zone at U, 0.2, a blue zone at R, 0.4 (linalool/Tl), and the terpene ester at R, - 0.65. 

The commercial oil sample 7 show.s three blue to red-violet terpene alcohols at R,0.2-0.3 a prominent violet-brown zone at R, 0.5 in the R, range of the carvon test (T3), two minor grey zones in the R, range of terpene esters (T3/linalyl acetate) and terpene zones at the solvent front. 

Terpene Esters by Direct Addition of Aliphatic Acids... 

Terpene esters can be made by the direct addition of fatty acids and halogenated and thiocyanated fatty acids to terpene hydrocarbons, ethers, and esters. Since the bicyclic terpimes (camphene, a-rpinene, and /3-pinene) are more reactive than the monocyclic, they are the preferable starting materials. 

Beyond the health benefits, we were motivated to investigate the role of PMFs on the citrus flavor profile. Although citrus flavor is usually associated with the more volatile terpenes, esters and aldeh des, it is well known that citrus flavors based upon volatile fractions can not entirely reproduce the flavor profile of citrus juices. We were interested to determine the role that PMFs played in the citms flavor profile. 

Acid-catalyzed hydration and acetoxylation of terpenes are important synthetic routes to terpenols and terpene esters that are used in perfumery and flavoring compositions. Such perfume ingredients as dihydromyrcenol (DHM-OH) and dihydro-myrcenyl acetate (DHM-OAc) are prepared by the hydration and acetoxylation of dihydromyrcene (DHM) (Scheme 6). 

In an analogous case (Eq. 62), the reaction of zinc acetate with f-butyl chloride in chloroform requires the presence of a PTC. The scope of this procedure was extended to the preparation of terpenic esters used as perfumes and flavors. 

The use of qualitative information alone is not suf cient to correctly characterize an essential oil, and quantitative data are of extreme importance. Classical methods are generally focused on chemical groups and the assessment of quantitative information through titration is widely applied, for example, for the acidimetric determination of saponi ed terpene esters. Saponi cation can be performed with heat, and in this case, readily saponi ed esters are to be investigated, in the cold, and afterward, the alkali excess is titrated with aqueous hydrochloric acid thereafter, the ester number can be calculated. A further test is the determination of terpene alcohols by acetylating with acetic anhydride part of the acetic anhydride is consumed in the reaction and can be quanti ed through titration of acetic acid with sodium hydroxide. The percentage of alcohol can then be calculated. The latter method is applied when the alcoholic constituents of an essential oil are not well known in case these are established, the oil is saponi ed, and the ester number of the acetylated oil is calculated and used to estimate the free alcohol content. 

Terpene esters constitute an important compound class in the essential oils. Acetate esters are those most frequently encountered more rarely, formates, propionates, butyrates, valerates and caprylates. Experience accumulated with over 30 different esters of lower fatty acids, shows that the zones on silica gel G layers, when developing with benzene or chloroform, are about 2.5 times higher than those of the corresponding alcohols (chamber saturation). Brud and Daniewski [28] have confirmed our finding [260] for loose silica gel layers also. The largest differences in hRf-values have been observed when using normal saturation (NS). 

Table 24. Separation of terpene esters on silica gel G layers...

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