Cata-Condensed Benzenoid Hydrocarbons

3 ENUMERATION OF KEKULE VALENCE STRUCTURES 2.3.1 Cata-Condensed Benzenoid Hydrocarbons 

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Fig. 3 Cata-condensed benzenoid hydrocarbons with more than one Clar structure...

Figure 2.8 shows how the experimentally observed wavelengths for two series of cata-condensed benzenoid hydrocarbons, the linearly annelated acenes and the angularly annelated phenes, change with increasing number of benzene rings. The shifts in the Lb and Bb positions are parallel to one another in both series, whereas the bathochromic shift of the Lj, band of acenes upon annelation is so pronounced that even in anthracene it masks the Lb band. 

Figure 5. Caterpillar graphs representing resonance pattern for n-sextets for several cata-condensed benzenoid hydrocarbons.

Balaban AT (1969) Chemical Graphs - VII - Proposed Nomendature of Branched Cata-Condensed Benzenoid Hydrocarbons. Tetrahedron 25 2949... 

Unbranched cata-condensed benzenoid hydrocarbons are structurally the simplest benzenoid hydrocarbons, for which holds the elegant algorithm of Gordon and Davison for enumeration of Kekuld valence structures. But can the algorithm of Gordon and Davison be extended to branched cata-condensed benzenoid hydrocarbons and peri-condensed benzenoid hydrocarbons ... 

The four-ring pyrene, as usually drawn, represents the smallest benzenoid lattice if we exclude cata-condensed benzenoid hydrocarbons. The peri-condensed benzenoids shown in Figure 2.6 illustrate additional smaller benzenoid lattices, which we use to introduce a generalization of the Gordon and Davison algorithm for counting... 

Simpson-Herndon model, and the conjugated-circuits model. The calculation of the KSC can be performed with recurrence relationships, matrix methods, and explicit combinatorial expressions derived for a large number of classes of conjugated hydrocarbons various classes of cata-condensed benzenoid hydrocarbons honeycomb lattice strips polymers. 

Definition A cata-condensed benzenoid hydrocarbon is a system built from fused benzene rings such that two adjacent rings have no other common adjacent rings. 

Figure 27. Cata-condensed benzenoid hydrocarbons with the maximal number of Kekule valence structures for a given number of fused benzene rings.

Figure 62. Cata-condensed benzenoid hydrocarbons having seven benzene rings. (RE values are shown in Table 23. ...

Table 23. Expressions for Molecular RE for a Selection of Cata-condensed Benzenoid Hydrocarbons Having Seven Fused Benzene Rings (Shown in Figure 62)...

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