Bicyclic Hydrocarbon Radicals

Form the names of simple acyclic, monocyclic, and bicyclic hydrocarbon terpene radicals systematically from the recommended names of the terpene hydrocarbons. For cyclic compounds, radicals may be formed with points of attachment in side chains which have a fixed numbering as well as in rings. Preference in numbering is given to the point of attachment over double bonds when there is a choice. 

The rules for naming bicyclic hydrocarbon terpene radicals are ... 

Rule 7 Form the above types of terpene-like names for all hydrocarbon terpene radicals derived from the four fundamental types of bicyclic hydrocarbons regardless of the position of the point or points of attachment that is, the H or H s may be removed from carbons in the ring or from carbons in the numbered side chains. Use position numbers to designate the position of the point or points of attachment in the radicals. 

Cyclic and Bicyclic Hydrocarbon ir-Radicals Prepared by Photolytic Method3... 

Among the simple cycloalkanes, we first discuss electron transfer from the three-to eight-membered cycloalkane prototypes to electron holes generated by radiolysis in different matrices, giving rise to the simple cycloalkane radical cations. Because of the significant interest they have attracted, the electron-transfer reactions of cyclopropane and, to a lesser extent, cyclobutane derivatives will be treated separately. Finally, electron transfer from some bicyclic hydrocarbons and the resulting radical cations will be discussed in a separate section (Section 2.4). 

In contrast with the highly strained bicyclic hydrocarbons containing three- and four-membered rings, the radical cations of bicyclic hydrocarbons containing five-membered or larger rings undergo electron transfer only reluctantly. As for simple... 

Reaction with unsaturated bicyclic hydrocarbons. From a study of the chlorination of unsaturated bicyclic compounds, Masson and Thuillier1 conclude that the reaction follows, a radical addition mechanism when initiated thermally or photo-chemically. The stereochemistry of the addition is markedly influenced by steric effects. No Wagner-Meerwein rearrangements are observed under these conditions. An ionic mechanism is involved without initiation or in the presence of trifluoroacetic acid in this case the usual carbonium ion rearrangements are observed. 

The dimer acids, DA, frequently represented as HOOC-D-COOH, are cyclic dibasic dimer having a total of 36 carbon atoms. The -D- represents a C34 hydrocarbon radical with one substituted cyclohexene structure [7,8]. Monocyclic dimer acids are obtained from dienoic acids while bicyclic structures have been found in fatty polymers of trienolic acids. Variation in structure of dimer acids from acyclic to polycyclic may be due to the involvement of different precursors for dimer preparation [9]. 

The through-space conjugation mode in 12.48 is called laticyclic. A number of systems have also been investigated here [66]. Definitive proof forthis type of overlap has been harder to come by. However, at least one class of bicyclic hydrocarbons has been shown to have large 7t—7i splittings [70] and more persuasively their radical cations have been shown to be delocalized by ESR spectrocopy [71]. 

System of Nomenclature for Hydrocarbon Terpene Radicals Acydics, Monocyclics, Bicyclics... 

No official action on the names of hydrocarbon terpene radicals was taken by the Nomenclature Committee of the ACS Organic Division at its meeting in New York City, September 1954, but general recommendations were discussed. It was agreed that the earlier acceptance of the system of nomenclature for the simple acyclic, monocyclic, and bicyclic terpene hydrocarbons implied the systematization of the hydrocarbon terpene radicals derived from these compounds. Therefore this Appendix F has been added here, but it has no official status. 

Table 1. Recommended General Names of Hydrocarbon Terpene Radicals for Acyclics, Monocyclics, and Bicyclics...

Rule 4 Form the names of bivalent radicals derived from the four fundamental types of saturated bicyclic terpene hydrocarbons and having the two points of attachment on the same carbon by adding "idene to the names of the saturated univalent radicals. The resulting names are thujylidene, carylidene, pinanyl-idene, bornylidene. If the bivalent radicals derived from the saturated structures have the two points of attachment on different carbon atoms, add "ene to the names of the saturated univalent radical names. The resulting names are thujylene, carylene, pinanylene, bomylene. 

Walk rearrangements have been observed in many carbo- and heterocyclic norcaradiene cycloheptatriene systems upon thermal as well as photochemical excitation. Table 4 contains selected examples. In this connection, the very different thermal stability of ll,ll-dimethyl-l,6-methano[10]annulene and its radical anion is worth mentioning (59). The neutral hydrocarbon rearranges to 7,7-dimethyl-l,2-benzocycloheptatriene at temperatures between 150 and 190°C [Table 4, entry 3, X = C(CH3)2 log A = UA Ea = 35.9 kcal/mol]. The corresponding rearrangement of the radical anion produced by reduction of the hydrocarbon with potassium occurs at -110°C already. The activation energy is lowered here by about 25 kcal/mol over that of the hydrocarbon. The norcaradiene walk has also gained some synthetic importance, for example, in the preparation of the unsaturated bicycle 44, a precursor of heptalene (60). 

Whereas the bicyclic sesquiterpene (— )-caryophyllene (159) [odor threshold in water solution 64ppb (77)] is widely distributed in flavors, its stereoisomer (160) is found only rarely in nature 206, 281, 336, 401). Apparently (160) is an artifact, the formation of which from (159) by the action of photochemically produced radicals could be shown (557). Black pepper oil rich in hydrocarbon (159) smells sweet and flowery 341, 500). On the other hand, the hydrocarbon fraction of... 

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