Terpenes Oxidation products

Calogirou, A., B. R. Larsen, and D. Kotzias, Gas-Phase Terpene Oxidation Products A Review, Atmos. Environ., 33, 1428-1439... 

CALOGIROU, A., LARSEN, B. R., KOTZIAS, D., Gas-phase terpene oxidation products A review, Atmos. Environ., 1999,33, 1423-1439. 

In addition to the important role biogenic terpenes play in gas-hase chemistry, their impact also extends to heterogeneous air chemistry. Although Went (1960) linked the formation of the blue haze over coniferous forests to the biogenic emission of 20 monoterpenes over 40 years ago, it was not until recently that terpenes received their due attention with respect to their role in secondary organic aerosol (SOA) formation. O Dowd et al. (2002) reported that nucleation events over a boreal forest were driven by the condensation of terpene oxidation products. Formaldehyde (HCHO) is a high-yield product of isoprene oxidation. The short photochemical lifetime of HCHO allows the observation of this trace gas to help constrain isoprene emissions (Shim et al. 2005). 

Sometimes, on account of the difiiculty in preparing the nitroso-chloride from a highly active o-pinene, it is necessary to examine the oxidation products before it is possible to come definitely to a conclusion as to the presence or absence of the hydrocarbon. Pinene yields numerous acids as the result of oxidising processes, so that the method of preparing the product to be examined must be rigidly adhei ed to if useful results are to be obtained. The terpene is transformed into pinonic acid, CjoHj Og, in the following manner A solution of 233... 

The oxidation products of camphene are of considerable interest, but as they vary very considerably according to the exact method of oxidation employed, they are not of very great use in the characterisation of the terpene. 

It results from the oxidation of sabinenic acid with peroxide of lead, sabinenic acid itself being an oxidation product of the terpene sabinene. It is a liquid having the following characters —... 

On a local or regional basis, terpenes may contribute significantly to oxidant problems (16,60,85,86,87, ), making control of anthropogenic hydrocarbons problematical. The question of relative controls on hydrocarbon and NOjj emissions from automobiles and industry has been a matter of longstanding controversy and debate in the US, particularly because of the potential role of biogenic hydrocarbons in oxidant production (16,89,90). This controversy is yet unresolved. 

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). 

Polyene cyclizations are of substantial value in the synthesis of polycyclic terpene natural products. These syntheses resemble the processes by which the polycyclic compounds are assembled in nature. The most dramatic example of biosynthesis of a polycyclic skeleton from a polyene intermediate is the conversion of squalene oxide to the steroid lanosterol. In the biological reaction, an enzyme not only to induces the cationic cyclization but also holds the substrate in a conformation corresponding to stereochemistry of the polycyclic product.17 In this case, the cyclization is terminated by a series of rearrangements. 

The synthesis of the Taxol in Scheme 13.56 by P. A. Wender and co-workers at Stanford University began with an oxidation product of the readily available terpene pinene. One of the key early steps was the photochemical rearrangement in Step B. 

Kleindienst, T.E., Harris, G.W., Pitts, Jr., J.N. (1982) Rates and temperature dependences of the reaction of hydroxyl radical with isoprene, its oxidation products, and selected terpenes. Environ. Sci. Technol. 16, 844-846. 

The cases where terpene metabolism has been studied In Insects are very few Indeed. Certain Ips and Dendroctonus bark beetles convert monoterpenes such as a-plnene, 6-plnene and myr-cene to oxidation products, some of which have pheromonal activities ( 5, 3A, 35). A Dendroc tonus bark beetle s cytochrome... 

Orange terpenes were emulsified in various carrier s and spray-dried. The spray-dried powders were aged for 3 days at 80 C in a draft oven. Beta-pinene is an oxidation product in orange terpenes which can be measured by GC. The beta-pinene level is proportional to the degree of oxidation of the orange terpenes. High levels of beta-pinene content in the spray-dried powders indicate poor oxidation resistance imparted to the encapsulated terpenes by the carrier. 

Another important aspect of encapsulation efficiency is the resistance to oxidation that the carrier imparts to the flavor oils. The oxidation resistance properties are critical to shelf-life stability of the encapsulated product. Oxidation properties can be measured organoleptically by a taste panel or by gas chromatograph of the recovered oil. Peaks related to oxidation products of orange terpenes obtained from GC analysis can be monitored as the powders are aged for three days at 80 C. The GC was used to measure beta-pinene, an oxidation product of orange terpenes. The results are reported in square inches. The greater the area for the beta-pinene peak, the poorer the oxidation resistance of carrier towards the orange terpenes. The data is presented in TABLE 5 ... 

Indoor Chemistry Various terpenes and terpenoids are emitted from household products and building materials. Ozone that has entered from outdoors or has been generated indoors can react with these compounds, either in the gas phase or on the surface of materials. The resulting oxidation products will contribute to the production and growth of meaningful quantities of secondary organic aerosols (SOA). The formation and growth of SOA can be studied under controlled conditions in test chambers (see also Chapter 13). 

Upper airway irritation of terpene/ozone oxidation products (TOPS). Dependence on reaction time, relative humidity and initial ozone concentration. Toxicology Letters, 143 (2), 109-14. 

Renwick J. A. A., Hughes P. R., Pitman G. B. and Vite J. P. (1976b) Oxidation products of terpenes identified from Dendroctonus and Ips bark beetles. J. Insect Physiol. 22, 725-727. 

The hydrocarbons of the various groups which we have just discussed are the true terpenes. On oxidation these yield alcohol and aldehyde or ketone derivatives. The olefine terpenes, only, yield aldehydes that occur as constituents of natural products known as essential oils (p. 840). The derivatives of both groups of cyclic terpenes which are present in essential oils and plant gums and resins are either secondary alcohols or ketones. Among these latter are the camphors of which common camphor is the most important and best known example. In a general sense all of the oxidation products of the cyclic terpenes are termed camphors. 

The preceding tabular scheme of the mono-cyclic terpenes and their oxidation products shows the relationships which we have been discussing. 

Two of the oxidation products of the terpene a-terpineol are terebic acid and terpenylic acid. Their structures were first established by the following synthesis ... 

Toxic gases and vapors (such as carbon monoxide and the partial oxidation products of terpenes) may be released in a fire involving turpentine. Turpentine attacks some coatings and some forms of plastic and rubber. 

Respiratory irritant mixtures can arise from environmental chemical reactions. For example, ozone reacts rapidly with terpenes under environmental ambient conditions to produce aldehydes, ketones, and carboxylic acids. Several studies that have been carried out demonstrated that reaction of ozone with a-pinene, c/-limonene, and isoprene produce low level concentrations (at or below NOEL levels) of oxidation products and that along with residual ozone and terpenes act as respiratory irritants. 1012 Table 17.3 lists the species typically contained in these mixtures along with their K values. As can be seen, the mixtures contain lipophiles (residual terpenes) and hydrophiles (the reaction products). Similar results have also been reported for environmental reaction of terpenes with ozone and nitrogen dioxide. 9 ... 

In the course of our studies on the microbial transformation of terpenes, this paper deals with the identification of oxidation products of 16 by Aspergillus niger and chemical conversion to biologically active compounds. 

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