Entropy difference between cis and trans configurations in crystalline fatty acids

Abstract

The dispersion curves of lattice and internal vibrations for two kinds of n-dodecanoic acid crystals composed of the cis and trans configurations, respectively, are calculated in a low frequency range below 500 cm −1. The entropy difference between the two kinds of crystal is estimated from the dispersion curves, and compared with that obtained previously. It is suggested that the main cause for the entropy difference between two isomers is the difference in the strength of the hydrogen bond, and that the weaker hydrogen bond produces the larger entropy.