On the relation between Zenkevich and Wiener indices of alkanes

A relatively complicated relation was found to exist between the quantity U recently introduced by Zenkevich (providing a measure of internal molecular energy), and the Wiener index W (measuring molecular surface area and intermolecular forces). We now report a detailed analysis of this relation and show that, in the case of alkanes, its main features are reproduced by the formula U = ??W + ? + ??1; where ?1 is the number of methyl groups, and ?, ? and ? are constants, depending only on the number of carbon atoms. Thus for isomeric alkanes with the same number of methyl groups, U and W are linearly correlated.