Effect of ethyl groups on the relation between Zenkevich and Wiener indices

Abstract

The Zenkevich index U provides a measure of the intramolecular energy of an organic molecule. The Wiener index W represents the surface area of the same molecules. Thus, from a physico-chemical point of view, no connection between U and W would be anticipated. Yet, in the case of alkanes. these two quantities depend on the same structural features of the molecular graph and an approximate mathematical relation between them can be established. Within sets of isomeric alkanes, the relation between U and W is linear, the (U W)-points forming several, mutually parallel, lines. Each such line pertains to a group of isomers possessing a fixed number of methyl and ethyl groups.