Conformational equilibrium of tetraethylammonium ion (Et
4N
+) 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 (Δ
Vtg.tg→tt.tt) between the
trans-gauche.trans-gauche (
tg.tg) and
trans-trans.trans-trans (
tt.tt) conformers of Et
4N
+ ion has been calculated from the pressure dependence of the relative Raman intensity ratio between the conformers. Δ
Vtg.tg→tt.tt is found to be negative throughout the studied concentration region. The value of Δ
Vtg.tg→tt.tt is the smallest in the methanol solution. The difference in the partial molar enthalpy (Δ
Htg.tg→tt.tt) is also estimated from the temperature dependence of the relative Raman intensity. From these results, we discuss the close relationship between the conformational change and the solvation structure.
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