Polycyclic aromatic hydrocarbons that we previously called total resonant sextet (TRS) benzenoids are revisited within the framework of recent experimental findings. A benzenoid transformation called leapfrogging generates TRS benzenoids. There are 13, 30, and 114 TRS benzenoid isomers with formulas C72H26, C96H30, and C102H32, respectively. “The leapfrogs of benzenoids are 2-factorable” is a s...

Using the formula periodic table for benzenoids (Table PAH6 = Table 1 in [4]) and the excised internal structure concept, several new strictly peri-condensed series possessing an identical number of isomers have been identified [5]. Strictly peri-condensed benzenoids have the property that the graph spanned by their internal carbon vertices (i.e., their excised internal structure) is connected....

G. Clar 6n Rule versus Hückel 4n + 2 Rule 3464 H. Hydrocarbons versus Heteroatomic Systems 3465 IV. Hidden Treasures of Kekulé Valence Structures 3466 A. Conjugated Circuits 3467 B. Innate Degree of Freedom 3470 C. Clar Structures 3472 V. Graph Theoretical Approach to Chemical Structure 3473 A. Metric 3473 B. Chemical Graphs 3473 C. Isospectral Graphs 3473 D. Embedded Graphs 3475 E. Partial Ord...

The main topological characteristics of altan-benzenoids were established. In particular, it was shown that the perimeter of Kekuléan altan-benzenoids is of size 4k , having a destablizing (anti-aromatic) energy effect, similar to (4k)-annulenes.

Despite the known biochemical production of a range of aromatic compounds by plants and the presence of benzenoids in floral scents, the emissions of only a few benzenoid compounds have been reported from the biosphere to the atmosphere. Here, using evidence from measurements at aircraft, ecosystem, tree, branch and leaf scales, with complementary isotopic labeling experiments, we show that veg...

In this note we present some new results on distances in benzenoids. An algorithm is presented which, for a given benzenoid system G bounded by a simple circuit 2 with n vertices, computes the Wiener index of G in O(n) time. Also we show that benzenoid systems have a convenient dismantling scheme, which can be derived by applying breadth-first search to their dual graphs. Our last result deals ...

The 1-, 2-, and 3-dimensional structures obtained from conjugated rings of carbon atoms are reviewed. They include finite small and large molecules (benzenoids, collarenes, beltenes, cyclacenes, cyclophenacenes, Möbius analogs, nanotori) and infinite macromolecules, nets and tilings (graphene, defected graphene, fractal benzenoids, nano-tubes, nano-cones, etc.). A few challenges for future expe...

In order to explore atomic asymmetry and molecular chirality in 2D space, benzenoids composed of 3 to 11 hexagons in 2D space were enumerated in our laboratory. These benzenoids are regarded as planar connected polyhexes and have no internal holes; that is, their internal regions are filled with hexagons. The produced dataset was composed of 357,968 benzenoids, including more than 14 million at...

The relationships between inner dual, dualist, sextet dualist, and antisextet dualist graphs and excised internal structures are fully delineated. It is proven that the antisextet dualist graph uniquely characterizes all strain-free benzenoids. At the same time, it is shown that the excised internal structure and dualist graph of the retro-leapfrog of all strain-free total resonant sextet benze...