Results 151 to 160 of about 8,344 (184)

Enumeration of benzenoid systems and other polyhexes

2005
The results of enumerations and classifications of polyhexes are reviewed and supplemented with new data. The numbers are collected in comprehensive tables and supplied with a thorough documentation from an extensive literature search. Numerous forms of the polyhexes are displayed, either as dualists or black silhouettes on the background of a ...
Björg N. Cyvin, Jon Brunvoll, Sven J. Cyvin   +2 more
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Topological properties of benzenoid systems

2005
The article reports investigations of the “topological” properties of benzenoid molecules which the author has performed in the last 20 years. Emphasis is given on recent developments and other scientists' contributions to these researches. Topics covered in recent books and reviews are avoided. The article outlines spectral properties, some aspects of
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Sombor Index and Elliptic Sombor Index of Benzenoid Systems

Match Communications in Mathematical and in Computer Chemistry
Summary: Let \(G\) be a graph with vertex set \(V\) and edge set \(E\). A topological index has the form \[ TI=TI(G)=\sum\limits_{uv\in E}f(d_G (u),d_G (v)), \] where \(f=f(x,y)\) is a pertinently chosen function which must be symmetric and real-valued for all \(x,y\) pertaining to vertex degrees of the graph \(G\).
Chen, Xiaohong, Wu, Baoyindureng, Li, Zhonghua   +2 more
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Rapid Ways to Recognize Kekuléan Benzenoid Systems

1990
This chapter presents rapid ways to determine whether or not a given benzenoid system possesses a Kekule structure. Two simple were discovered by Sachs and the present author, respectively. Both algorithms operate by deleting vertices and edges from the benzenoid system examined. Emphasis is given to the algorithm proposed by the present author.
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Non-Kekuléan and Essentially Disconnected Benzenoid Systems

1988
In the present chapter we outline the basic facts about those benzenoids which are not normal. As already explained in Paragraph 2.3.2 these are the non-Kekulean systems (for which no Kekule structure can be drawn) and the essentially disconnected systems (which possess fixed single or double bonds).
S. J. Cyvin, I. Gutman
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Global Forcing Numbers of Handgun-shaped Benzenoid Systems

Current Nanoscience, 2014
Let G be a molecular graph with bond set E(G) that admits a Kekulé structure. A global forcing set of G is any subset of E(G) such that no two Kekulé structures of G coincide on S. The number of bonds in a global forcing set of the smallest cardinality is called the global forcing number of G.
Xiu-Song Liu, Shou-Jun Xu, Liangping Tu
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Reduced (a, b)-KA Indices of Benzenoid Systems

Annals of Pure and Applied Mathematics, 2021
Topological indices are applied to measure the chemical characteristics of chemical compounds. This study computes the reduced (a, b)-KA indices of benzenoid systems. Also, we obtain some other reduced graph indices directly as special values of a and b.
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ChemInform Abstract: Clar Polynomials of Large Benzenoid Systems.

ChemInform, 1998
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
M. RANDIC, S. EL‐BASIL, S. NIKOLIC, N. TRINAJSTIC   +3 more
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The Directed Lithiation of Benzenoid Aromatic Systems

European Journal of Inorganic Chemistry, 2003
AbstractDirected metallation using organolithium bases is one of the best ways of regiospecifically elaborating aromatic systems and their substituents. For benzenoid arenes, deprotonation occurs at the ortho, lateral or peri positions. The reasons for each type of reaction will be considered in the context of the propensities of different directing ...
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The existence of Kekulé structures in a benzenoid system

1990
The existence of Kekule structures in a benzenoid system is the first fundamental problem in the topological theory of benzenoid systems. It was considered as one of the most difficult open problems in this theory. Many investigations have been made in order to find necessary and sufficient conditions for the existence of Kekule structures in a ...
Zhang, F. J., Guo, X. F., Chen, R. S.
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