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.