How far are molecular connectivity descriptors from I(S) molecular pseudoconnectivity descriptors?

A comparison of the characteristics of the molecular connectivity and intrinsic-state pseudoconnectivity indices in modeling different activities and properties of different classes of compounds is performed. Two different activities of chlorofluorocarbons, an activity of 2-Br-2-phenetylamines, an activity of benzimidazoles, and the boiling points of primary amines and primary alcohols are modeled. The simultaneous modeling of these last two classes of compounds is also accomplished. The comparison encompasses also the molar mass as descriptor. Further, the influence of the rescaling procedure on the modeling for the case of benzimidazoles is analyzed as well as the relationship between degeneracy of connectivity values and quality of the modeling. Molecular pseudoconnectivity terms seem to compete advantageously with molecular connectivity terms in the descriptive power of the activity and property of many classes of compounds. In many cases new mixed higher-order connectivity-pseudoconnectivity terms have been detected that consistently improve the quality of the description.