Alicyclic compounds, aromatization

This chapter consists of four sections viz Aliphatic Compounds, Alicyclic Compounds, Aromatic Compounds and Heterocyclic Compounds. 

This chapter consists of five sections viz Aliphatic Compounds, Alicyclic Compounds, Aromatic Compounds, Heterocyclic Compounds and MisceUaneous As, B, P, Si, S, Se, and Te Compounds. 

Kovats, E. and A. Wehrli (1959), Gas-chromatography characterization of organic compounds. III. Calculation of the retention indexes of aliphatic, alicyclic and aromatic compounds . Helv. Chim. Acta, Vol. 42, p. 2709. 

Carbocyclic compounds are very usefully divided into (a) saturated (alicyclic) compounds, (b) aromatic compounds and (c) the intermediate partially unsaturated (alicyclic) compounds. Heterocyclic compounds can be subdivided in exactly the same way, and equally usefully. 

The hydroxamic acid function in most alicyclic and aromatic compounds is stable to hot dilute acid or alkali, and derivatives cannot undergo normal base-catalyzed Lessen rearrangement. Di Maio and Tardella," however, have shown that some alicyclic hydroxamic acids when treated with polyphosphoric acid (PPA) at 176°-195° undergo loss of CO, CO.2, or H2O, in a series of reactions which must involve earlj fission of the N—0 bond, presumably in a phosphoryl-ated intermediate. Thus, l-hydroxy-2- piperidone(108) gave carbon monoxide, 1-pyrroline (119), and the lactams (120 and 121). The saturated lactam is believed to be derived from disproportionation of the unsaturated lactam. 

As the preceding section correctly suggests, aromatic rings a-hound in compounds that show biologic activity. The reasons for this are many the role of the pi electrons in some form of charge transfer complex ranks among the more Important. There ire few monocyclic alicyclic compounds known that are used as medicinal agents. 

Other polynuclear hydrocarbons may include bridged hydrocarbons, spiro hydrocarbons, mixed systems containing alicyclic and aromatic rings, and aliphatic chains, etc. Examples may be found in the CRC Handbook [63, Section C]. Physical properties of selected polynuclear aromatic compounds are given in [49, p. 967]. 

Halogenated derivatives of the same kind are much more radiation resistant for aromatic than for alicyclic compounds. The resulting order is aromatic > ionic > alicyclic. Even when the... 

Koch J, G Fuchs (1992) Enzymatic reduction of benzoyl-CoA to alicyclic compounds, a key reaction in anaerobic aromatic metabolism. Eur J Biochem 205 195-202. 

Further exploitation of the molecular shape feature has led more recently to the design of another series of clathrate hosts by substituting on the allene rigid backbone bulky groups 22>, Representative compounds of this new host family are 20 and 21. The allene 20 (R = t-butyl) shows an interesting clathration behaviour upon crystallization from various environments, including alicyclic and aromatic compounds, heterocycles, cyclic ketones and eyclohexaneamine 26>. 

The allene host 20 exhibits high inclusion selectivity in competition experiments using mixtures of solvents 26). In fact, preliminary results indicate that it can be used for the separation of constitutional isomers, of homologues, and of aliphatic from alicyclic or aromatic compounds (Table 3). Other derivatives of the allene, e.g. 21, are also functional as host molecules, and are currently being subjected to further investigations 22). 

Kishi, H., Kogure, N., Hashimoto, Y. (1990) Contribution of soil constituents in adsorption coefficient of aromatic compounds, halogenated alicyclic and aromatic compounds to soil. Chemosphere 21, 867-876. 

Rule of thumb The stability of molecular ions roughly decreases in the following order aromatic compounds > conjugated alkenes > alkenes > alicyclic compounds > carbonyl compounds > linear alkanes > ethers > esters > amines > carboxylic acids > alcohols > branched alkanes. [81]... 

Hydrocarbons. Compounds consisting of carbon and hydrogen. The number of such compounds is immense and they may be classified into aliphatic (alicyclic) and aromatic (cyclic) compounds. In the former class, the principal carbon atoms are arranged in chains, while in the latter class they are arranged in one or several rings. Hydrocarbons may also be divided into saturated —in which all four valences of C are satisfied, and unsaturated —in which there are one or more double or triple bonds between carbon atoms... 

Aromatization of alicyclic compounds. Cyclohexane carboxylic acids maybe metabolized by a mitochondrial enzyme system to an aromatic acid such as benzoic acid. This enzyme system requires CoA, ATP, and oxygen and is thought to involve three sequential dehydrogenation steps after the initial formation of the cyclohexanoyl CoA (Fig. 4.36). The aromatase enzyme also requires the cofactor FAD. 

The Hammett relationship formalizes and puts into quantitative terms much of the qualitative reasoning we have used for reactions involving aliphatic, alicyclic, and aromatic compounds. Considerable effort has been made to extend the Hammett idea to cover reactions other than of meta- and para-substituted benzene derivatives, but these will not be discussed here.1... 

The methods of preparation which are considered in this chapter involve, principally, ring-forming reactions leading to a restricted and subjective selection of various typical and interesting heterocyclic systems. These cyclic systems may be classified as (a) saturated or partly unsaturated heterocyclic, or (b) heteroaromatic, according to their physical, chemical and spectroscopic properties and to the reactivity of the functional groups attached to the ring atoms. In this way such properties and reactivity are broadly related to those of alicyclic and aromatic compounds. 

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