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Ivan Gutman

Publications and source records attributed to Ivan Gutman.

3 recordsLinked to original sources

Chirality codes and molecular structure.

Some time ago a structure-descriptor, named "chirality code", was put forward [J. Chem. Inf. Comput. Sci. 2001, 41, 369-375], aimed at distinguishing between enantiomers. The chirality code is a sequence of (typically 100) numbers, being equal to the value of a certain "chirality function" at equidistant points within a chosen interval. For molecules of moderate size the chirality function has thousands of peaks (maxima and minima), one for each quartet of atoms. Therefore it looks as if the chirality code cannot provide a faithful representation of the chirality function and thus a faithful representation of the molecular structure. We now show that functional groups present in the molecule result in clusters of near-lying and partially overlapping peaks, whose position in the chirality code is characteristic for the particular functional group. This enables a sound structural interpretation of the chirality code.

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Algebraic Kekulé structures of benzenoid hydrocarbons.

An algebraic Kekulé structure of a benzenoid hydrocarbon is obtained from an ordinary Kekulé structure by inscribing into each hexagon the number of pi-electrons which (according to this Kekulé structure) belong to this hexagon. We show that in the case of catafusenes, there is a one-to-one correspondence between ordinary and algebraic Kekulé structures. On the other hand, in the case of perifusenes, one algebraic Kekulé structure may correspond to several ordinary Kekulé structures.

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Variable neighborhood search for extremal graphs. 10. Comparison of irregularity indices for chemical trees.

Chemical graphs, as other ones, are regular if all their vertices have the same degree. Otherwise, they are irregular, and it is of interest to measure their irregularity both for descriptive purposes and for QSAR/QSPR studies. Three indices have been proposed in the literature for that purpose: those of Collatz-Sinogowitz, of Albertson, and of Bell's variance of degrees. We study their properties for the case of chemical trees. Structural conjectures are generated with the system AutoGraphiX, and most of them proved later by mathematical means. Analytical expressions for extremal values are obtained, and extremal graphs are characterized for the two last indices.

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