Hydrocarbon ring assemblies

Table 2 Three heterocyclic rings fused (5 5 6)—types of hydrocarbon ring assembly.

Unbranched assemblies consisting of three or more identical hydrocarbon ring systems are named by placing an appropriate numerical prefix before the name of the hydrocarbon corresponding to the repetitive unit. The following numerical prefixes are used ... 

Univalent and multivalent radicals derived from assemblies of identical hydrocarbon ring systems are named by adding -yl , ylene or -diyl , -triyl , etc., to the name of the ring assembly. 

From the assemblies of fused five- and six-membered rings identifiable on the surface of 1, corannulene (8) is the smallest fragment that retains a bowl-shaped conformation. However, there are other known hydrocarbons that adopt bowl (or... 

We earlier recalled that one can build a huge number of molecules by simply assembling CeH rings, a scheme that was summarized in Table 1.4, and that a solid such as graphite can be obtained in this gedanken synthesis. Let us briefly discuss the case of linear acenes, which are linear polycyclic aromatic hydrocarbons (PAHs) composed of laterally fused CeHe rings. 

The self-assembly of CD rotaxanes is expected on account of the strongly pronounced ability of CDs to form inclusion complexes with organic molecules. In principle, any through-ring CD complex can be considered as a pseudorotaxane. Thus, polymethylene compounds, terminated with appropriate end groups such as pyridinium, [14] bipyridinium, [15] or carboxyl groups [16] could form rather stable complexes with a-CD where the hydrocarbon chain is located inside the CD cavity. 

Electrocyclic ring closures of acyclic trienes and tetraenes have substantial negative entropies of activation, as anticipated for reactions in which rotational freedom is lost on assembling the cyclic transition states. Conversions of the more rigid cyclic trienes and tetraenes to bicyclic hydrocarbons usually have less negative entropies of activation. 

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