A Dielectric Spectroscopic Study of Ethylene Carbonate in Solution

作者:Sagawa Naoya; Takabatake Shunzo; Shikata Toshiyuki*
来源:Bulletin of the Chemical Society of Japan, 2016, 89(9): 1018-1025.
DOI:10.1246/bcsj.20160126

摘要

The formation of anti-parallel dimers ((EC) 2) of ethylene carbonate (EC) in solution is discussed via dielectric data determined over a frequency range up to 3 THz. Two major dielectric processes have been identified in both benzene (Bz) and dimethyl carbonate (DMC) solutions. The relaxation times were ca. 8 and ca. 20 ps in Bz, and ca. 20 and ca. 40 ps in DMC solution for the two relaxation processes, respectively. The population of monomeric EC was evaluated from the strength of the faster relaxation mode assigned to the rotational mode of monomeric EC. Equilibrium constants (K-d) for the (EC)(2) formation in the two solvents were determined as functions of the concentration at room temperature assuming a process, 2EC reversible arrow (EC)(2). The libration of EC molecules was observed as a sharper resonance signal at ca. 1.5 x 10(13) s(-1) when they existed as monomeric EC rather than in the form of (EC) 2 in Bz, whereas the signal was not so sharp in DMC. The fact that the determined Kd values depended on the solvent: 3-7 M-1 in Bz and 0.05-0.1 M-1 in DMC, reveals that the choice of solvent governs the efficiency of (EC) 2 formation. The Kd showed reasonable agreement with the previously determined equilibrium constants using Raman scattering techniques.

  • 出版日期2016-9-15