Larger Terpenes

The larger terpenes are formed in the same manner as the monoterpenes and sesquiterpenes. The precursor for the diterpenes is the C2o compound geranylgeranyl pyrophosphate, which is formed from farnesyl pyrophosphate in a manner similar to that shown in Figure 28.2 ... 

About 3000 different molecules are used in the F F industry. Approximately half of them, mostly terpenes, are included in the FEMA (Flavor and Extracts Manufacturing Association) and FDA lists. However, only a few hundred compounds are used in larger than ton quantities. Terpenes constitute the vast majority of the aroma chemicals. They are obtained either by... 

As discussed in Chapter 9.C.2, some of the larger alkenes such as terpenes form particles containing low-volatility organics on oxidation with ozone. Hence particle formation might be expected indoors in the presence of such compounds, and indeed this has been observed (Weschler and Shields, 1999). 

Sterols are derivatives of terpenes, within the larger chemical family of terpenoids. Such compounds are widespread and numerous in eukaryotes. Although in many cases their function is not clear, others are known to have an essential role in growth, development, metabolism and the integrity of cells. Sterols are localised in cell membranes, conferring stability and controlling permeability. 

The monocyclic terpene hydrocarbons, many of which are formed readily from the acyclic terpenes by ring closure or from the bicyclic terpenes by ring fission, contain a six-carbon ring and may all be considered as derivatives of either cyclohexane or benzene. They may also be classified, on the basis of common larger fundamental structures, into two distinct types of substituted six-carbon ring structures ... 

For systematizing the nomenclature of bicyclic terpene hydrocarbons, a consideration of only the fundamental parent carbon skeletons larger than the unsubstituted ring systems (Chart 8) is not adequate. The fundamental unsubstituted parent ring... 

The recommended systematic names of the thujane, carane, and pinane bicyclic hydrocarbons are formed from the common terpene names of the saturated fundamental structures larger than the unsubstituted ring systems. Where these do not apply, the nor- forms of these terpene names are recommended for the carane and pinane types of structures, and the bicyclo names for the thujane type. For purposes of uniformity and convenience, skeletal formulas resembling the familiar terpene formulas are used they are oriented so that the isolated methyl group is at the top and the numbering runs clockwise. The general rules for forming the names are ... 

Rule 2. Retain the names thujane, carane, and pinane for the fundamental saturated structures larger than the unsubptituted ring systems, and form series of names based on these common terpene names. 

Rule 1. Use the name norbomane for the fundamental saturated ring system, which is bicyclo[]2.2.1]] heptane. Use the name bornane for the saturated larger parent compound, which is 1,7,7-trimethylbicyclo[]2.2.1]] heptane. Form a series of names based on these two new terpene names. 

In this work we report organic and elemental carbon data, l C content and 13c/12c isotopic ratios for samples obtained in a larger set of measurements in the POLTERCAIST (POLlutant-TERpene CAnopy Interaction STudy) taken at the Walker Branch experimental site, Oak Ridge National Laboratory, Oak Ridge, TN, during a summer period (July, 1983) and a late winter period (March,... 

Essential oil produced by supercritical carbon dioxide extraction is more similar to that present in the living plant, i.e. more top notes, a higher proportion of esters and some larger molecules. However, the presence of fewer terpenes may be due to their lower solubility in the carbon dioxide compared with conventional organic solvents. 

Many other reactions give even larger and more complex terpenes with a variety of functionalization but we will treat only one group in detail. These compounds are so important to us that they are given a different name. 

Worth, and Jeffries (211) obtained emissions 2 to 10 times larger than any previous estimate. Rasmussen (199) has concluded that, while the identity of the emissions is well known, a quantitative estimate of the worldwide terpene emission rate is not yet possible. It would appear that the natural emissions are much larger than that estimated for man s activities, 27 x 10 tons yr Ripperton et al. have suggested that the reaction of ozone with terpenes provides an important, if not dominant, sink for both compounds in the troposphere. While large terpene mixing ratios (ppm or more) have been measured locally in isolated areas [Ripperton et al. (211)], no global estimate is available. 

Olefine and Cyclic Terpenes.—Two distinct groups are known which have entirely different structure. The first and smaller group includes strictly aliphatic hydrocarbons belonging to the olefine or ethylene unsaturated series. The second group, which is much larger, includes cyclo-aliphatic hydrocarbons or as we have previously described them the hydro-aromatic hydrocarbons. Thus we have ... 

As each of these menthenes will yield isomeric mentha di-enes the number of isomers possible in this group is still larger. That is, one men-thane yields six menthenes and these a larger number, viz., fourteen, mentha-di-enes. Furthermore, stereo-isomerism with accompanying optical activity due to the presence of asymmetric carbons, increases the number of possible isomers. It will not be necessary to dwell further upon the isomerism of the terpenes it being necessary simply to explain the fact of the existence of structural isomers and of stereo-isomers with optical activity. The system of nomenclature of the isomers will not be considered. Reference to larger books will be necessary to make this plain. 

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