Carnelley's Rule and the Prediction of Melting Point

Carnelley (1882) made some important and useful observations on the relationship between the arrangement of the atoms in a molecule and its melting point. According to Brown and Brown (2000. J Chem Ed 77:724-731), Carnelley's rule states of two or more isometric compounds, those whose atoms are the more symmetrically and the more compactly arranged melt higher than those in which the atomic arrangement is asymmetrical or in the form of long chains. Carnelley's rule can best be understood and quantitated from the dependence of the entropy of melting upon molecular geometry. (C) 2014 Wiley Periodicals, Inc. and the American Pharmacists Association