title: The sum-connectivity index--an additive variant of the Randic connectivity index.
abstract: This review discusses structure-property modeling applications of a novel variant of the Randic connectivity index that is called the sum-connectivity index. We compare published one-descriptor quantitative structure-property relationship (QSPR) models obtained with the new sum-connectivity index and with the Randic connectivity index, called here the product-connectivity index. Additionally, the efficiency of both variants of connectivity indices in QSPR modeling is tested on five datasets of alkanes and two datasets of polycyclic hydrocarbons. Several physicochemical properties of alkanes (i.e. boiling and melting points, retention index, molar volume, molar refraction, heat of vaporization, standard Gibbs energy of formation, critical temperature, critical pressure, surface tension, density) and &#960;- electronic energies of two sets of polycyclic hydrocarbons were correlated with the product- and sum-connectivity indices. A comparison of these QSPR models shows that both variants of connectivity indices are equivalent, and only slightly (but not significantly) better results are obtained with the sum-connectivity index. Inter-correlations between the product- and sum-connectivity indices are mostly linear with a slope very close to 1.0 for alkanes, and with a slope more different from 1.0 (0.88) for polycyclic compounds. The comparative analysis presented here supports the use of the sumconnectivity index in QSPR/QSAR studies together with the product-connectivity index. Further studies on larger and more heterogeneous datasets should test the sum-connectivity index in QSPR/QSAR models.
authors.affiliation: NMR Center, The Ruđer Boskovic Institute, PO Box 180, HR 10 002 Zagreb, Croatia. lucic@irb.hr
authors.forename: Bono
authors.initials: B
authors.lastname: Lučić
authors.forename: Ivan
authors.initials: I
authors.lastname: Sović
authors.forename: Jadranko
authors.initials: J
authors.lastname: Batista
authors.forename: Karolj
authors.initials: K
authors.lastname: Skala
authors.forename: Dejan
authors.initials: D
authors.lastname: Plavšić
authors.forename: Drazen
authors.initials: D
authors.lastname: Vikić-Topić
authors.forename: Drago
authors.initials: D
authors.lastname: Bešlo
authors.forename: Sonja
authors.initials: S
authors.lastname: Nikolić
authors.forename: Nenad
authors.initials: N
authors.lastname: Trinajstić
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D003196:Computer Graphics; D008956:Models, Chemical; D011083:Polycyclic Compounds / Q000737:chemistry*; D021281:Quantitative Structure-Activity Relationship
chemical_list: D000473:Alkanes; D011083:Polycyclic Compounds