Carbon skeleton, identification

Identification of 9,12-tetradecadienyl (9,12-14) compounds began with studies on two cosmopolitan pests of stored products, the almond moth (Cadra cmtella, Pyralidae Phycitinae) and the Indian meal moth (Plodia interpunctella, Phycitinae) [38,39]. This 9,12-14 structure has been reported from another 13 Pyralidae (only in Phycitinae) species and 11 Noctuidae species (9 species in Amphipyrinae, and 1 species each in Hadeninae and Plusiinae). These two families, however, are not closely related. Most likely, the females classified in distant groups happened to produce the same chemical in the train of their perpetual evolution of modifying the original systems for pheromone biosynthesis. The 5,7-dodecadienyl (5,7-12) structure is a carbon skeleton common... 

Each pair of connected carbon atoms, CA — CB, is thus segregated according to its sum of chemical shifts, so that the actual magnitude of the carbon-carbon coupling constant is no longer required for identification of the bond. A straightforward method of tracing out the carbon skeleton of a compound is thus established. 

The Prefix Nor Is Used to Denote a Ring System Devoid of Methyl Groups. The Identification Numbers for the Formulas Correspond to Those Used in Later Charts. The Orientations Shown in Column 1 are Only for Ready Recognition of the Corresponding Larger Bicyclic Carbon Skeletons Recommended in Chart 8. 

Bothe, H., Darley, D. J., Albracht, S. P., Gerfen, G. J., Golding, B. T., and Buckel, W., 1998, Identification of the 4-glutamyl radical as an intermediate in the carbon skeleton rearrangement catalyzed by coenzyme Bi2-dependent glutamate mutase from Clostridium cochlearium. Biochemistry 37 4105n4113. 

T c.e identification and naming of functional groups is more important than the naming of cotnpwunds. This was your chance to experiment with different functional groups as well as different carbon skeletons. 

Kohnen M.E.L., Sinninghe Damste J.S., ten Haven H.L., Koch-van Dalen A.C., Schouten S., de Leeuw J.W. (1991c) Identification and geochemical significance of cyclic di-and trisulphides with linear and acyclic isoprenoid carbon skeletons in immature sediments. Geochim. Cosmochim. Acta 55, 3685-95. 

Enzymes catalyzing carbon skeleton rearrangements were the first to be recognized as coenzyme B 12-dependent. The first was glutamate mutase (GM), discovered in 1960, and the nature of the skeletal rearrangement in the reaction of GM inspired the identification of coenzyme B12 as the coenzyme for the apparently similar reaction of... 

The tasks formulated above have determined the structure of the book, the first six chapters of which are devoted to accounts of the main chemical methods (preliminary processing of samples, kinetic methods, pyrolysis GC, determination of carbon skeleton, subtraction method, chemically selective stationary phases, elemental analysis). The last two chapters are devoted to the solution of two tasks that are most important in analytical chemistry nowadays the determination of impurities (Chapter 8) and the identification of components of complex mixtures by fimctional group analysis (Chapter... 

In the determination of the carbon skeleton, thoroughly elaborated reaction methods associated with the participation of hydrogen are most often used. In the literature (e.g., ref. 1) the methods for determining the carbon skeleton are considered only on the basis of this reaction. However, for determining the carbon skeleton, other reactions can also be employed successfully, although their field of application is narrower. Thus, methylation is valuable for the identification of hydrocarbons (see Chapter 1). Diazomethane reacts under strong ultraviolet irradiation in the cold in accordance with the following equation ... 

An example of the power of this method in structural elucidation is shown for the sesquiterpene lactone acetyhsomontanohde (Fig. 5.77). The complete carbon skeleton of the molecule can be traced directly in the spectrum, with breakdown occurring only when heteroatom linkages arise. Unfortunately, it is rare indeed to have sufficient sample quantities at hand to consider employing this technique, and still it remains of limited application in its original form. Nevertheless, in very proton-sparse systems, it may present the only option as in the identification of the nitration product of 5.11a. The product was to... 

Cubitermes umbratus is an example of a termite using the second type defense. Soldiers produce four diterpenes, biflora-4,10 (19)-15-triene (156) (522), cembrane A (157) and 3-Z-cembrane A (158) (521) and cubitene (159). More recently, isolation and identification of cube-gene (160), a diterpene with a novel carbon skeleton from C. ugandensis soldiers, has been reported (539). Odontotermes badius also bites with... 

The identification of terpenoic compounds is very complicated because these substances usually occur in mixtures of closely related compounds, and they are sensitive to various kinds of isomerization and to the rearrangement of the carbon skeleton. Gas chromatography (GC) has proved to be the most useful and fastest method of separating the terpenes in complex mixtures substantial progress has been achieved after making use of capillary columns. The very complex nature of many essential oils does not allow a complete chromatographic separation even on high-resolution columns. 

An elegant modern method of identification of the basic carbon skeleton consists in pyrolysis in the presence of hydrogen combined with gas chromatography, which is mainly stiitable for aliphatic compounds (56—58). The necessary equipment is conunercially available (59). 

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