AB-INITIO CALCULATIONS OF SUBSTITUENT CONSTANTS - A REINVESTIGATION

A set of various substituent constants sigma(F), sigma(R), sigma(alpha ), and sigma(chi) for 21 common substituents was recalculated accordin g to the models of Marriott and Topsom which are based on ab initio ca lculations. Some inconsistencies in the original methods as to the use of molecular geometries and basis sets were eliminated and a few valu es of the original work were corrected. The set was extended by an add itional 10 substituents derived from the amido and thioamido groups, w ith particular interest for QSAR. Comparison with standard experimenta l data confirmed the physical meaning and significance of the computat ional model for sigma(F), sigma(R), sigma(alpha), but not for sigma(ch i). (C) 1997 Elsevier Science B.V.