Predicting the total entropy of melting: application to pharmaceuticals and environmentally relevant compounds
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Updated: Oct 20, 2026

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients
Published on: August 9, 2022
R M Dannenfelser1, S H Yalkowsky
1Novartis Pharmaceutical Corporation, 59 Route 10, East Hanover, New Jersey 07936, USA. rosemary.dannenfelser@novartis.com
Abstract:
Experimental entropy of melting values for physical property estimation schemes, such as solubility and vapor pressure, are not readily available. In this study a semiempirical equation, which contains two molecular parameters, is used to estimate the total entropy of melting for a variety of pharmaceutically and environmentally relevant compounds. A database of experimental entropy values consisting of over 370 different compounds was compiled from literature. A molecular rotational symmetry number and a molecular flexibility number for each compound were defined. The simple equation does very well in predicting the total entropy of melting for the complex set of molecules with an average error of 21%.
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