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

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 ΔG and the entropy difference ΔS 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.