Polycyclic Alicyclics

C6H8+- C5H40+- HBr+ C5H6N+ cyclohexenes, polycyclic alicyclics cyclopentenones bromo compounds pyrroles, pyridines... 

H 14n 11 211-2 alkenes, monocycloalkanes, alkynes, dienes, cycloalkenes, polycyclic alicyclics, cyclic alcohols... 

H 14n alkanes, alkenes, monocycloalkanes, alkynes, dimes, cycloalkmes, polycyclic alicyclics, alkanones, alkanals, glycols, glycol ethers, alkyl chlorides, add ehlorides... 

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

Alicyclic dianhydrides are interesting for electronic applications. The polyimides obtained from them are colorless with high transparency in the visible range, exhibit low birefringence,125 and have a low dielectric constant.126 The reactivity of the polycyclic aliphatic dianhydride has been investigated. For example, bicyclo-[2,2,2]-oct-7-ene tetracarboxylic dianhydride reacts quickly with an aromatic amine because the bicyclo-imide is less strained than the corresponding dianhydride.127... 

The aerobic degradation of cycloalkanes has been examined in both monocyclic and polycyclic snb-strates. In all of them, monooxygenation is the first step and this is sometimes accomplished by cytochrome P450 systems. Reviews of the degradation of alicyclic componnds inclnding monoterpenes... 

Polycyclic oxetanes are obtained in good yields in intramolecular carbonyl-olefin cycloadditions, in an analogous way as the corresponding alicyclic systems are formed in intramolecular enone-olefin additions. Two applications are given in (4.78)492) and in (4.79)493). 

Dehydrogenation (the conversion of alicyclic or hydroaromatic compounds into their aromatic counterparts by removal of hydrogen and also, in some cases, of other atoms or groups) finds wide application in the determination of structure of natural products of complex hydroaromatic structure. Dehydrogenation is employed also for the synthesis of polycyclic hydrocarbons and their derivatives from the readily accessible synthetic hydroaromatio compounds. A very simple example is the formation of p-methylnaphthalene from a-tetra-lone (which is itself prepared from benzene—see Section IV, 143) ... 

Univalent radicals derived from ortho-fused or ortho- and peri-fused polycyclic hydrocarbons with names ending in -ene by removal of a hydrogen atom from an aromatic or alicyclic ring are named in principle by changing the ending -ene of the names of the hydrocarbons to -enyl . 

The importance of these three classes of unsaturated compounds is that they contain many naturally occurring examples having specific biological activity. For this reason their general methods of synthesis are of interest. Furthermore, their particular functional features are to be found embedded in the structures of more complex acyclic, alicyclic and polycyclic molecules. Thus the incorporation of the simpler structures as building blocks in multistage syntheses of, for example, antibiotics has been one of the synthetic challenges of recent decades. 

Benzene (1) is the simplest aromatic hydrocarbon upon which our knowledge of aromatic chemistry is based. This hydrocarbon, the alkylbenzenes (2), the arylmethanes [e.g. diphenylmethane (3)], the biphenyls [e.g. biphenyl (4)] and the condensed polycyclic systems [e.g. naphthalene (5) and anthracene (6)] all exhibit chemical reactivity and spectroscopic features which are markedly different from their aliphatic and alicyclic hydrocarbon counterparts. Indeed the term aromatic character was introduced to specify the chemistry of this group of hydrocarbons and their substituted functional derivatives, and it was soon used to summarise the properties of certain groups of heterocyclic compounds having five- and six-membered ring systems and the associated condensed polycyclic analogues (Chapter 8). 

Another extension is in the field of alicyclic compounds (7, 112). In steroid compounds it has been proved that long-distance effects, e.g. from position 17 to 3 and vice versa, affect polarographic half-wave potentials. Finally it has been demonstrated (7, 113) that Hammett and Taft substituent constants can be used as a first approximation to express the substituent effects in numerous types of mono- and polycyclic heterocyclic compounds. 

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