Modified Trouton's rule for predicting the entropy of boiling

Simple modifications of Trouton's rule for estimating the entropy of boiling of organic compounds are presented. An empirical equation is developed which expresses the entropy of boiling as a function of molecular flexibility and hydrogen bonding. This equation, which enables the simple yet reasonable estimate of entropy of boiling directly from molecular structure, was generated from a training set of 850 structurally diverse compounds. The average absolute percent error for a test set of 88 compounds is 2.5% which is more accurate than Trouton's rule.