Molecular connectivity. III: Relationship to partition coefficients.

The molecular connectivity index is shown to be linearly related to the octanol-water partition coefficients of a variety of monofunctional chemical classes including esters, alcohol, ketones, ethers, carboxylic acids, amines, and hydrocarbons. A modification of the connectivity index, taking into account the valency or degree of unsaturation of an atom, merges the data for all compounds except hydrocarbons. The connectivity index is also shown to be useful for correlating biological activity. These studies indicate that partition coefficients represent empirical quantities having intermediate significance between biological data and the more fundamental property of molecular connectivity.