Revisiting the formation of cyclic clusters in liquid ethanol

摘要

The liquid phase of ethanol in pure and in non-polar solvents was studied at room temperature using Fourier transform infrared (FT-IR) and H-1 nuclear magnetic resonance (NMR) spectroscopies together with theoretical approach. The FT-IR spectra for pure ethanol and solution in cyclohexane at different dilution stages are consistent with H-1 NMR results. The results from both methods were best explained by the results of the density functional theory based on a multimeric model. It is suggested that cyclic trimers and tetramers are dominated in the solution of cyclohexane/hexane with the concentration greater than 0.5M at room temperature. In liquid ethanol, while the primary components at room temperature are cyclic trimers and tetramers, there is a certain amount (similar to 14%) of open hydroxide group representing the existence of chain like structures in the equilibria. The cyclic cluster model in the liquid and concentrated solution phase (>0.5M) can be used to explain the anomalously lower freezing point of ethanol (159 K) than that of water (273 K) at ambient conditions. In addition, H-1 NMR at various dilution stages reveals the dynamics for the formation of cyclic clusters. Published by AIP Publishing.