Statistical mechanics of small chain molecules in liquids. II. Intermolecular pair correlations for liquid n-butane

Abstract

In this article the intermolecular structure of liquid n‐butane is studied with an application of the RISM integral equation. It is found that the pair correlations between atoms in different n‐butane molecules do depend upon the nature of the intramolecular trans–gauche conformational equilibrium. An incorrect picture of the liquid structure is obtained if it is assumed that the fluid is composed only of trans conformers—the species most favored energetically. The local packing of CH₃ and CH₂ groups in the liquid is discussed. Particular attention is focused on the prediction of the Chandler–Pratt theory, which says that steric effects produce a solvent shift in conformational equilibria in liquid n‐butane. It is shown that x‐ray diffraction experiments can provide a direct probe of this phenomenon.