I have been trying to calculate the molecular connectivity indices for Cis-butadiene and Trans-butadiene given as 1.9908 and 1.9558 on page 141 of Concepts and applications of molecular similarity, by Mark A. Johnson and Gerald M. Maggiora, eds., John Wiley & Sons, New York, 1990, in the chapter entitled, “Design of Molecules with Desired Properties” as I have not been able to reproduce these values. In the article “Development of 3-Dimensional Molecular Descriptors”, Computers Chem. Vol. 14, No. 3, pp. 237-246, 1990, Randic, Jerman-Blazic and Trinajstic, prescribe starting with the geometric distance matrix “as an input and for each CC distance the appropriate weight is found using 1/(mn)1/2, where m and n are the valencies of the atoms making up each bond”. I have tried multiplying each entry of the geometric distance matrix by this weighting factor and proceeding in the same manner as with the adjacency matrix to obtain the atomic path numbers and molecular path number, P1, the molecular connectivity. I have also tried various combinations of the weighting factor for various CC distances . I would like to know what I am doing wrong here and would appreciate any help you are willing to provide.
I do not have access to this book chapter and, hence, cannot see whether Johnson and Maggiora have provided specifics on how their connectivity indices were calculated. So, I just wanted to warn you that "conectivity index" is a generic name for a broad family of molecular descriptors. It is quite possible that Johnson/Maggiora and Randic et al do not mean the same index.
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