Mean Molecular Radius and the Wiener Number: A Quest for Meaning

Sa？etak The Wiener number (W) and its cubic root (W1/3) were correlated with molecular radii (radius of gyration, s, and the mean molecular radius, rm) of 14 homologous sets of straight-chain and branched alkanes, with 1–21 carbon atoms. From the linear regression equations of s, s2 and s3 on W, it can be concluded that the best results in terms of the correlation coefficient (r2 = 0.9906–1.0000), as well as in terms of other regression parameters, were obtained with the response variable s3. This means that the Wiener number is most appropriately interpreted as molecular volume. Linear regression of s on W1/3 gave similar results (r2 = 0.9885–0.9994), suggesting W1/3 should be interpreted as a molecular radius. The differences between the regression coefficient and regression parameters are more pronounced for less branched molecules. Analogous linear regressions of the mean molecular radius, rm, differ little from the regressions of s