A DIFFERENTIAL MOLECULAR CONNECTIVITY INDEX

A differential molecular connectivity index, DELTA-(m)X, has been defined which is the difference between the simple and the valence connectivity indexes of the same order, m, is DELTA-(m)X = (m)X - (m)X(v). The information contained in this index is largely electronic with contributions from adjacent alkyl fragments amounting to the size of m. The electronic information is a quantitation of the pi and lone pair electrons on that part of the fragment defined by m. The index is capable of modeling selected physical properties which are regiospecific within a molecule. Examples include NMR chemical shifts, gas phase basicities, ionization potentials and chromatographic retention indexes.