3D WEIGHTING OF MOLECULAR DESCRIPTORS FOR QSPR QSAR BY THE METHOD OF IDEAL SYMMETRY (MIS) - 1 - APPLICATION TO BOILING POINTS OF ALKANES/

The method of ideal symmetry (MIS), developed recently, presents molec ules as systems of mutually repulsing atoms connected by covalent bond s of constant length. In this paper we have used MIS optimized geometr y to define a vertex 3D weight as a metric analogue of the vertex dist ance sum in molecular graphs. These 3D weights were used as a substitu te for the vertex degrees in several well known topological (2D) indic es, thus producing a series of 3D-weighted molecular descriptors. The novel indices were tested in calculating the boiling points of a serie s of 73 C3-C9 alkanes and showed generally a better performance than t he original 2D indices. The best 1-, 2-, and 3-variable linear regress ion models incorporated 3D zero-order molecular connectivity with corr elation coefficients of 0.9892, 0.9961, and 0.9986, and standard devia tions of 5.97, 3.64, and 2.17 degrees C, respectively. The approach wa s further validated by correlations with four other properties of alka nes (heats of formation, heats of vaporization, heats of atomization, and molar volume). The potential of the proposed 3D weighting of topol ogical indices for QSPR/QSAR studies was thus demonstrated. (C) 1998 E lsevier Science B.V.