The trans/gauche conformational equilibrium and associated thermodynamic parameters of liquid 1,2-dibromoethane as studied by infrared electroabsorption spectroscopy

Abstract

Infrared electroabsorption spectroscopy is used to study the trans/gauche conformational equilibrium and associated thermodynamic parameters of the two conformers of liquid 1,2-dibromoethane at room temperature. Electric-field modulation induces an increase in the population of the gauche conformer that has the permanent dipole moment and a decrease in that of the trans conformer that has a center of inversion symmetry and hence no dipole moment. The Gibbs free energy difference DG and the entropy difference Delta S between the gauche and trans conformers are obtained as 4.5 kJ mol(-1) and -2.7 J K(-1) mol(-1), respectively, using the reported enthalpy difference. (C) 2008 Elsevier B. V. All rights reserved.