Kinetic steric factors and connectivity indices

In this study the relationships between previously reported connectivity indices described by Kier and Hall and steric contributions to the rate constants for several series of reactions are examined. Rate data were examined for four different series of reactions, which were chosen to represent a range of different reaction mechanisms and transition-state structures. For sterically controlled reactions, the relative rates of series of substrates can be correlated either with the connectivity indices of the substrates themselves or with the changes in the indices that accompany formation of transition states. As expected, the significant indices in the correlations are of the cluster and path-cluster types. The connectivity indices should be useful descriptors in helping relate equilibrium properties, chemical reactivities, and pharmacological data to one another.