نتایج جستجو برای: benzenoid chain

تعداد نتایج: 295963  

2012
IVAN GUTMAN

1031 Vertex-degree-based molecular structure descriptors of benzenoid systems and phenylenes IVAN GUTMAN* and BORIS FURTULA** Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia (Received 12 December 2011) Abstract. Several recently published papers report expressions for various vertex-degree-based molecular structure descriptors of benzenoid systems and phenyl...

Journal: :Faraday discussions 2007
Patrick Bultinck

A large number of local aromaticity indices for the benzenoid rings in polyaromatic hydrocarbons is computed. The results are interpreted, supporting Clar's hypothesis, and mutual correlations are investigated. It is shown that there are good correlations between all indices that strictly allow comparing benzenoid character. Poor correlations are found with NICS. A rationale is offered, yieldin...

2007
Ivan Gutman Slavko Radenković

A structure-descriptor EE, recently proposed by Estrada, is examined. If λ1, λ2, . . . ,λn are the eigenvalues of the molecular graph, then EE = n ∑ i=1 eλi . In the case of benzenoid hydrocarbons with n carbon atoms and m carbon-carbon bonds, EE is found to be accurately approximated by means of the formula a1 n cosh (√ 2m/n ) +a2, where a1 ≈ 1.098 and a2 =−0.64 are empirically determined fitt...

Journal: :Zeitschrift fur Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie 1972
G Schöllnhammer P Hemmerich

It has been shown by TE NIJENHUIS and BERENDS2 that the benzenoid (or better: o-quinoid) subnucleus of alloxazines can be attacked photochemically. We found that with flavins the reaction products bear a hydroxyl group either in the 6 or in the 9 position of the benzenoid nucleus. The reactive species is the protonated flavin, the rate of the reaction has an optimum at pH 0 — 1. At still lower ...

Journal: :Discrete Mathematics 1998
Victor Chepoi Sandi Klavzar

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 ...

Journal: :iranian journal of mathematical chemistry 2012
i. gutman

a recently published paper [t. došlić, this journal 3 (2012) 25-34] considers the zagrebindices of benzenoid systems, and points out their low discriminativity. we show thatanalogous results hold for a variety of vertex-degree-based molecular structure descriptorsthat are being studied in contemporary mathematical chemistry. we also show that theseresults are straightforwardly obtained by using...

Journal: :Proyecciones (Antofagasta) 2019

2007
Ivan Gutman Peter Paule

We predict the number of hexagonal systems consisting of 24 and 25 hexagons to be H 24 = 122237774262384 and H 25 = 606259305418149, with 6 and 5 signiicant digits, respectively. Further estimates for H n up to n = 31 are also given. Informally speaking, a hexagonal system can be viewed as a connected arrangement of hexagonal cells packed in the same way as the typical honeycomb arrangement in ...

2004
Ivan Gutman Peter Paule

We predict the number of hexagonal systems consisting of and hexagons to be H and H with and signi cant digits respectively Further estimates for Hn up to n are also given Hexagonal Systems Informally speaking a hexagonal system can be viewed as a connected arrangement of hexagonal cells packed in the same way as the typical honeycomb arrangement in a bee hive More formally it is a nite connect...

2004200520062007200820092010201120122013201420152016201720182019202020212022202305000100001500020000

نمودار تعداد نتایج جستجو در هر سال

با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید