A modification of Trouton's rule by simple molecular parameters for hydrocarbon compounds

The entropy of vaporization at the normal boiling point (Delta S-b) is an i mportant propel ty in the chemical engineering and environmental sciences. This paper presents a simple modification of Trouton's rule to estimate thi s property for a variety of hydrocarbon compounds including alkanes, alkene s, alkynes, dienes, cycloalkanes, and alkyl aromatics. The equation contain s three easy-to-determine parameters that describe important molecular feat ures: flexibility, symmetry, and planarity. The entropy data were calculate d from experimental enthalpy data of 477 different organic compounds at the normal boiling point. The average percentage error for the prediction is 1 .30 by the proposed method, 2.79 by Trouton's rule, 1.62 by Kistiakowsky's method, 1.51 by Vetere's method, and 2.23 by the group contribution method of Ma and Zhao.