Current status of isomer enumeration of practical benzenoids

Experimental and Theoretical Approach To Determine the Average Asphaltene Structure of a Crude Oil from the Golden Lane (Faja de Oro) of Mexico

“…The absolute cata -condensed systems have P C = 0%; these are the least compact systems. For cata -condensed systems, C Y is always zero. c See refs and . d Number of resonant sextets in the structure. Each sextet comprises 6 π electrons. e Number of localized double bonds.…”

The Most Stable Class of Benzenoid Hydrocarbons and Their Topological Characteristics − Total Resonant Sextet Benzenoids Revisited

“…benzenoids are totally isomorphic; (7) the formula periodic tables and constant-isomer series for strictly pericondensed and strain-free TRS benzenoids are totally isomorphic; the leapfrog algorithm associates any given benzenoid with its TRS isomorph. [8][9][10][11]13 LEAPFROG ALGORITHM Application of the leapfrog algorithm on all noncatacondensed benzenoid isomer sets culled of members with catacondensed appendages (benzo, naphtho, etc.) or bridging units (like that in zethrene) and four or more adjacent bay regions will generate all possible isomeric strain-free TRS benzenoids; strain-free TRS benzenoids have nonhelical structures devoid of adjacent bay regions.…”

“…11,13 Both the C 54 H 26 and C 78 H 26 structures are first-generation members of the respective TRS constant-isomer series that possess a one-to-one matching in point group symmetry among the four isomers per our previously published topological paradigm. [7][8][9][10][11]13 Figure 4 depicts the 13 C 72 H 26 TRS benzenoid structures for the first time, but this isomer number has been published. 11 The D 2h isomer (first structure in Figure 4) synthesized by Mullen and co-workers 4 is the leapfrog of a ds + NIc ) r -2; ds ) net disconnections of internal edges, NIc ) no.…”

“…Symmetry between the base excised internal structure (EIS) and its successors is preserved when one successively circumscribes with hexagonal rings to ultimately generate constant-isomer series. Previously, it was demonstrated that there exists a one-to-one correspondence between the constant-isomer benzenoid series generated by the circumscribing process and TRS constant-isomer series generated by an augmented circumscribing process. − Circumscribing benzene with a string of 18 connected carbons with 6 hydrogens gives coronene (C 24 H 12 ); benzene is called the excised internal structure of coronene. Circumscribing coronene gives circum(30)coronene (C 54 H 18 ), and circumscribing this circumcoronene gives dicircum(30,42)coronene (C 96 H 24 ).…”

“…Mullen and co-workers have recently synthesized large to super-large benzenoid hydrocarbons − of the type that we have previously called total resonant sextet (TRS) benzenoids, − and this success has revived our interest in these systems. In 1987, we enumerated and compiled a list of large benzenoid isomers that were presumed to be capable of being structurally characterized once detected in the environment or synthesized .…”