Chemical Equilibria Studied by Infrared Electroabsorption Spectroscopy: From a Simple Liquid to a Complex Water/Oil Suspension

• Main Authors: Lee, I-Chun, 李依純
• Other Authors: Shigeto, Shinsuke
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/94058598747302222366

碩士 === 國立交通大學 === 分子科學研究所 === 97 === Infrared (IR) electroabsorption spectroscopy is used to study chemical equilibria of the two condensed-phase systems: liquid 1,2-dibromoethane and water in reverse micelles. First, we report on experimental determination of thermodynamic parameters associated with the gauche/trans conformational equilibrium of liquid 1,2-dibromoethane. The equilibrium constant at room temperature was determined to be 0.33 (±0.04), which indicates that the trans conformer is energetically more favored than the gauche conformer. With the reported value of the enthalpy difference , we obtained the Gibbs free energy difference and the entropy difference between the two conformers as 4.5 (±0.3) kJ mol−1 and −2.7 J K−1 mol−1, respectively. In the second system, we measured IR electroabsorption spectra in the OH stretching region of water in aerosol OT reverse micelles. The observed IR electroabsorption spectrum shows a bipolar feature with intensity moving from the red to the blue. The OH stretching absorption band is deconvoluted to three Gaussian subbands, which correspond to distinct hydrogen-bonding environments. The IR electroabsorption spectrum may be interpreted in terms of a field-induced population change among those three kinds of water molecules, which are assumed to occur in equilibrium.