Higher Terpenes

Terpenes, Higher alcohols. Acetals, acids, alcohols, ketones. ... 

Tail to tail linkages of isoprene units sometimes occur especially m the higher terpenes The C(12)—C(13) bond of squalene unites two C15 units m a tail to tail man ner Notice however that isoprene units are joined head to tail within each C15 unit of squalene... 

The higher terpenes are formed not by successive addition of C5 units but by the coupling of simpler terpenes Thus the triterpenes (C30) are derived from two mole cules of farnesyl pyrophosphate and the tetraterpenes (C40) from two molecules of ger anylgeranyl pyrophosphate These carbon-carbon bond forming processes involve tail to tail couplings and proceed by a more complicated mechanism than that just described... 

Chemical iajections iato piae trees have been reported to have stimulatory effects on the natural production of resias and terpenes and may result ia high yields of these valuable chemicals. Combiaed oleoresin—timber production ia mixed stands of piae and timber trees is under development, and it appears that when short-rotation forestry is used, the yields of energy products and timber can be substantially higher than the yields from separate operations. 

Gum Elemi. This resin, tapped from trees in the Philippines, contains a higher concentration of essential oils than other natural resins. It is a soft, sticky, plastic material that can be deformed manually. Gum elemi [9000-75-3] contains 20—25% essential oils, 13—19% acids, 30—35% resenes (condensed decarboxylated resin acids), and 20—25% terpenic resinols (condensed terpene alcohols). It has an acid number of 20—35 and a saponification number of 20—40. Gum elemi is a film-forming plasticizing resin used in lacquers. 

The price of natural citral from Utsea cubeba in 1995 was 17.60—18.70/kg and the price of terpene-based synthetic citral was for 6.60—8.80/kg (69). Higher grades of synthetic citral are available for flavor and fragrance uses and price largely depends on the quaUty and quantity purchased. Shipment of citral is usually made in lined dmms, pails, or aluminum cans. 

L. Ruzicka (Zurich) work on polymethylenes and higher terpenes. 

Terpenes (and terpenoids) are further classified according to the number of 5-carbon units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, diterpenes are 20-carbon substances from four isoprene units, and so on. Monoterpenes and sesquiterpenes are found primarily in plants, but the higher terpenoids occur in both plants and animals, and many have important biological roles. The triterpenoid lanosterol, for example, is the precursor from which all steroid hormones are made. 

It is immediately clear that Acanthomyops need not rely on dietary sources of terpenes but can synthesize citronellal and citral from either acetate or mevalonate. The higher total activity of the citronellal as compared with the citral probably reflects the natural preponderance of citronellal (ca. 90%) in the ant secretion. As the specific activities show, these results are consistent with a common biogenetic origin of both terpenes. In the mevalonic acid pathway as described from other organisms (13), the radioactive carbon of l-C14-mevalonate is lost upon formation of isopentenyl pyrophosphate. 

Explicit mechanisms attempt to include all nonmethane hydrocarbons believed present in the system with an explicit representation of their known chemical reactions. Atmospheric simulation experiments with controlled NMHC concentrations can be used to develop explicit mechanisms. Examples of these are Leone and Seinfeld (164), Hough (165) and Atkinson et al (169). Rate constants for homogeneous (gas-phase) reactions and photolytic processes are fairly well established for many NMHC. Most of the lower alkanes and alkenes have been extensively studied, and the reactions of the higher family members, although little studied, should be comparable to the lower members of the family. Terpenes and aromatic hydrocarbons, on the other hand, are still inadequately understood, in spite of considerable experimental effort. Parameterization of NMHC chemistry results when NMHC s known to be present in the atmosphere are not explicitly incorporated into the mechanism, but rather are assigned to augment the concentration of NMHC s of similar chemical nature which the... 

Wall Loss of Oxidation Products. It is known that some classes of hydrocarbons (the higher terpenes, for instance) are prolific aerosol formers when subjected to atmospheric oxidation. Other classes, aromatic hydrocarbons for instance, although they do not form large amounts of suspended aerosol, have been shown to lose (at least under some conditions) large amounts of oxidation products to the reaction vessel walls. The fate of these oxidation products in the open atmosphere remains open to question, as does the extent to which they continue to participate in gas-phase chemistry (187). 

Other observations on chemical variation within Zieria can be mentioned at this point. Zieria cytisoides form b occurs along the coast of New South Wales and in similar habitats in Tasmania. Five populations concern us here, two from the former area and three from the latter. Significant differences in the concentration of the mono-terpene derivative (-)-chrysanthenone [37] were observed by Southwell and Armstrong (1987). The populations on the mainland exhibited concentrations of the ketone of 15% and 18%, whereas those in Tasmania had higher amounts, that is, 42%, 49%, and 55%. The New Caledonian Z. chevalieri was shown to exhibit an unusual profile of compounds, relative to the Australian species, with 2,4,6-trimethoxystyrene [38],... 

The use of nitrogen fertilization results in higher content of N-containing compounds, including free amino acids, and also increases in terpene content in wood plants, whilst starch, total carbohydrates, phenylpropanoids and total carbon-based phytochemicals decreased (Koricheva et al., 1998). Higher levels of nitrogen favoured its uptake and increased the nitrate content of the crop, which is critical for salad vegetables and baby foods. 

Hydroxy-4,4,6-trimethyl-2,5-hexadien-l-one, lanierone, 254, is a component of the complex aggregation signal of male Ipspini [468]. The carbon skeleton of 254 is the same as in isophorone 255, which has been identified as a volatile constituents of females of Ips typographus. Whether these compounds are degradation products of higher terpenes awaits further investigations. 

---