Conformational Equilibrium of the Tetraethylammonium Ion in Alcohols
Yukihiro YOSHIMURA, Takefumi GOTO, Machiko SHIGEMI and Takahiro TAKEKIYO
Abstract:Conformational equilibrium of tetraethylammonium ion (Et4N+) in alcohols (methanol, ethanol, n-propanol) has been investigated by Raman spectroscopy as functions of concentration, pressure and temperature. The difference in the partial molar volume (ΔVtg.tg→tt.tt) between the trans-gauche.trans-gauche (tg.tg) and trans-trans.trans-trans (tt.tt) conformers of Et4N+ ion has been calculated from the pressure dependence of the relative Raman intensity ratio between the conformers. ΔVtg.tg→tt.tt is found to be negative throughout the studied concentration region. The value ofΔVtg.tg→tt.tt is the smallest in the methanol solution. The difference in the partial molar enthalpy (ΔHtg.tg→tt.tt) is also estimated from the temperautre dependence of the relative Raman intensity. From these results, we discuss the close relationship between the conformational change and the solvation structure. Key Words:Conformation, Tetraethylammonium ion, Alcohol solutions, Raman spectroscopy