Jerry Ray Dias

A periodic table for polycyclic aromatic hydrocarbons. Isomer enumeration of fused polycyclic aromatic hydrocarbons. Part I

a few people, however, who recognize a need to use the system but, for reasons of their own, choose to have a search intermediary do it for them or at least work with them on a graphical search session. At this point, therefore, it appears that the role of the search specialist has evolved away from searches originated by individual users (except in a few cases) who now can and should run their own searches, toward a function which satisfies information needs at project team and management levels.

A periodic table for polycyclic aromatic hydrocarbons. IV. Isomer enumeration of polycyclic conjugated hydrocarbons. 2

Additional work toward systematizing all polycyclic aromatic hydrocarbons (PAHs) into a unified, comprehensive data and information package by using graph theoretical principles is described. Key equations [N,, + d, = constant and Npc = NH - 6 + 3r3 + 2r4 + r5 - r7 - 2r8 - 3r9 - -a] are illustrated in the enumeration of all 43 totally fused polycyclic conjugated hydrocarbon isomers of anthracene. The practical molecular size limit of the PAH6 formula periodic table was investigated. The largest literature reported PAHs are Cs8HSo (from pitch), C62H34, C64H32, C66H36, C68H34, and C72H36 (theoretical studies). All PAH6s with the same number of formula hydrogens (NH) have structures with the same carbon atom perimeter length (qp = 2NH - 6 = constant) and lie along the same diagonal formula array in the PAH6 formula periodic table. The maximum number of alkynyl units (A,=) in addition to benzenoid rings that can exist in a molecular structure corresponding to a PAH6 formula is given by A,,, I (1/4)(2N, - ~NH + 6). An algorithm for determining the maximum number of alkyl methylene carbons that a structure corresponding to a PAH6 formula can possess is presented. The number of benzenoid PAH6 isomers having formulas C38H16, CmH16, C42H16, C48H18, CSOH18, C52H18, and C60HZO are 10,3, 1,22,7,2, and 19, respectively; a method for their complete enumeration is presented. The area of polycyclic conjugated hydrocarbons needing future research emphasis has been identified. and methods for selective literature searching with PAH formulas is presented. In this fourth paper of the series’-3 the current and past research scope of polycyclic aromatic hydrocarbons (PAHs) is examined within the framework of graph theoretical principles. Additional graph theoretical algorithms and correlations have been developed for inclusion of alkyl-substituted and alkynyl-containing PAH6s. One eventual goal of this work is to develop a unified, comprehensive data and information package for all PAHs systematized according to Table I and the principles developed in this series.

Benzenoid series having a constant number of isomers. 3.: total resonant sextet Bezenoids and their topological characteristics

Two distinct classes of benzenoid groups having a constant number of isomers have been identified for the total resonant sextet isomer subset. One class is topologically unique and the other forms a pairwise topologically equivalent class. The numbers of isomers in these two classes are the same as those reported in Part 2 of this series for strictly peri-condensed benzenoids. This correspondence clearly signals the discovery of a fundamental topological paradigm

Studies in deciphering the information content of chemical formulas: a comprehensive study of fluorenes and fluoranthenes

By use of a formula periodic table, the aufbau principle, and the excised internal structure concept an important subset of fluorenes and fluoranthenes are enumerated. Constant-isomer series for these compounds are presented for the first time. These results illustrate the generality of the previously developed algorithm and associated concepts. These results are summarized within the background of known fluorene-related heterocycles and fluoranthene hydrocarbons. Structural/theoretical properties of these compounds are detailed.

Benzenoid series having a constant number of isomers. 2. Topological characteristics of strictly peri-condensed constant-isomer benzenoid series

für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Topological Characteristics of Strictly Pericondensed Constant-Isomer Benzenoid Series

Benzenoid series having a constant number of isomers

In addition to a timely review of benzenoid quinones, equations for counting the number of benzenoid quinones are presented. A comparison of the number of benzenoid monoquinone isomers theoretically possible versus the number reported in the chemical literature provides us with a unique perspective of this important group of compounds. If the excised internal structure of a benzenoid hydrocarbon has only one KekuW structure ( K = 1) and no more than two methylene groups, then one of the monoquinone isomers of that benzenoid will also have K = 1. Within the HMO approximation for h = k = 1 for oxygen, if a monoquinone and its benzenoid precursor both have the same number of KekulE structures, then the quinone has LUMO = 0.

Notes on constant-isomer series

Constant-isomer series are polycyclic aromatic hydrocarbon sets having equal numbers of isomers. While presenting an overview of constant-isomer series, general algebraic formulations of our previous results on polycyclic hydrocarbons are reported. Numerous interrelationships and properties of specific representatives are presented. The underlying similarity relationships covered by our topological paradigm provides the unifying framework for this paper. Formulas of constant-isomers correspond to fewer types of structures.

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

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 stronger statement than “the leapfrogs of benzenoids are closed-shell.”

Determining the Number of Resonance Structures in Concealed Non-Kekuléan Benzenoid Hydrocarbons

The number of resonance structures (SC) for previously published concealed non-Kekuléan benzenoid hydrocarbons is determined. Using a simple computer program, analytical expressions for determining SC for various classes of non-Kekuléan (free-radical) benzenoid hydrocarbons are derived, and some properties of concealed non-Kekuléan benzenoid hydrocarbons are studied.

Two-Dimensional Arrays in the Analysis of Trends in Series of Molecules: Strongly Subspectral Molecular Graphs, Formula Periodic Tables, and Number of Resonance Structures

Two-dimensional arrays consisting of strongly subspectral molecular graphs and formula periodic tables for polycyclic aromatic hydrocarbons are briefly reviewed. New two-dimensional arrays for free-radical benzenoid hydrocarbons are presented with general analytical expressions for counting their number of resonance structures (SC). The structural origin of the coefficients to these analytical expressions is discussed.